Constants documentation and 3 fixed scaladoc bugs

The REPL :java -app command is a convenience to locate
the body of DelayedInit code.  Now it will look for
new style delayedEndpoints on the class before it
falls back to showing the apply method of the
delayedInit$body closure.

```
apm@mara:~/tmp$ skala
Welcome to Scala version 2.11.0-20130711-153246-eb1c3137f5 (OpenJDK 64-Bit Server VM, Java 1.7.0_21).
Type in expressions to have them evaluated.
Type :help for more information.

scala> :javap -pv -app delayed.C
  public final void delayedEndpoint$delayed$C$1();
    flags: ACC_PUBLIC, ACC_FINAL
    Code:
      stack=2, locals=1, args_size=1
         0: getstatic     scala#29                 // Field scala/Predef$.MODULE$:Lscala/Predef$;
         3: ldc           scala#31                 // String this is the initialization code of C
         5: invokevirtual scala#35                 // Method scala/Predef$.println:(Ljava/lang/Object;)V
         8: return
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
               0       9     0  this   Ldelayed/C;
      LineNumberTable:
        line 11: 0

scala> :q
apm@mara:~/tmp$ rm delayed/*.class
apm@mara:~/tmp$ scalac delayed.scala
apm@mara:~/tmp$ skala
Welcome to Scala version 2.11.0-20130711-153246-eb1c3137f5 (OpenJDK 64-Bit Server VM, Java 1.7.0_21).
Type in expressions to have them evaluated.
Type :help for more information.

scala> :javap -pv -app delayed.C
  public final java.lang.Object apply();
    flags: ACC_PUBLIC, ACC_FINAL
    Code:
      stack=2, locals=1, args_size=1
         0: getstatic     scala#13                 // Field scala/Predef$.MODULE$:Lscala/Predef$;
         3: ldc           scala#15                 // String this is the initialization code of C
         5: invokevirtual scala#19                 // Method scala/Predef$.println:(Ljava/lang/Object;)V
         8: getstatic     scala#25                 // Field scala/runtime/BoxedUnit.UNIT:Lscala/runtime/BoxedUnit;
        11: areturn
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
               0      12     0  this   Ldelayed/C$delayedInit$body;
      LineNumberTable:
        line 11: 0
        line 10: 8
```

SI-8128 Fix regression in extractors returning existentials

Test locally built scala parser-combinators classes.

SIP-23 Account for literal types in varargs translation

Top level modules in Scala currently desugar as:

```
class C; object O extends C { toString }
```

```
public final class O$ extends C {
  public static final O$ MODULE$;

  public static {};
    Code:
       0: new           #2                  // class O$
       3: invokespecial #12                 // Method "<init>":()V
       6: return

  private O$();
    Code:
       0: aload_0
       1: invokespecial #13                 // Method C."<init>":()V
       4: aload_0
       5: putstatic     #15                 // Field MODULE$:LO$;
       8: aload_0
       9: invokevirtual #21                 // Method java/lang/Object.toString:()Ljava/lang/String;
      12: pop
      13: return
}
```

The static initalizer `<clinit>` calls the constructor `<init>`, which
invokes superclass constructor, assigns `MODULE$= this`, and then runs
the remainder of the object's constructor (`toString` in the example
above.)

It turns out that this relies on a bug in the JVM's verifier: assignment to a
static final must occur lexically within the <clinit>, not from within `<init>`
(even if the latter is happens to be called by the former).

I'd like to move the assignment to <clinit> but that would
change behaviour of "benign" cyclic references between modules.

Example:

```
package p1; class CC { def foo = O.bar}; object O {new CC().foo; def bar = println(1)};

// Exiting paste mode, now interpreting.

scala> p1.O
1
```

This relies on the way that we assign MODULE$ field after the super class constructors
are finished, but before the rest of the module constructor is called.

Instead, this commit removes the ACC_FINAL bit from the field. It actually wasn't
behaving as final at all, precisely the issue that the stricter verifier
now alerts us to.

```
scala> :paste -raw
// Entering paste mode (ctrl-D to finish)

package p1; object O

// Exiting paste mode, now interpreting.

scala> val O1 = p1.O
O1: p1.O.type = p1.O$@ee7d9f1

scala> scala.reflect.ensureAccessible(p1.O.getClass.getDeclaredConstructor()).newInstance()
res0: p1.O.type = p1.O$@64cee07

scala> O1 eq p1.O
res1: Boolean = false
```

We will still achieve safe publication of the assignment to other threads
by virtue of the fact that `<clinit>` is executed within the scope of
an initlization lock, as specified by:

  https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-5.html#jvms-5.5

Fixes scala/scala-dev#SD-194

Abstract away all the things

Non local returns aren't eliminated after inlined in 2.11 or 2.12

```
⚡ scala
Welcome to Scala 2.12.1 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_112).
Type in expressions for evaluation. Or try :help.

scala> @inlune def foo(a: => Any) = if ("".isEmpty) a else ""
<console>:11: error: not found: type inlune
       @inlune def foo(a: => Any) = if ("".isEmpty) a else ""
        ^

scala> @inline def foo(a: => Any) = if ("".isEmpty) a else ""
foo: (a: => Any)Any

scala> class InlineReturn { def test: Any = foo(return "") }
defined class InlineReturn

scala> :javap -c InlineReturn#test
  public java.lang.Object test();
    Code:
       0: new           #4                  // class java/lang/Object
       3: dup
       4: invokespecial #32                 // Method java/lang/Object."<init>":()V
       7: astore_1
       8: getstatic     #36                 // Field $line4/$read$$iw$$iw$.MODULE$:L$line4/$read$$iw$$iw$;
      11: aload_1
      12: invokedynamic #59,  0             // InvokeDynamic #0:apply:(Ljava/lang/Object;)Lscala/Function0;
      17: invokevirtual #63                 // Method $line4/$read$$iw$$iw$.foo:(Lscala/Function0;)Ljava/lang/Object;
      20: goto          44
      23: astore_2
      24: aload_2
      25: invokevirtual #66                 // Method scala/runtime/NonLocalReturnControl.key:()Ljava/lang/Object;
      28: aload_1
      29: if_acmpne     39
      32: aload_2
      33: invokevirtual #69                 // Method scala/runtime/NonLocalReturnControl.value:()Ljava/lang/Object;
      36: goto          41
      39: aload_2
      40: athrow
      41: goto          44
      44: areturn
    Exception table:
       from    to  target type
           8    20    23   Class scala/runtime/NonLocalReturnControl
```

```
⚡ ~/scala/2.11.8/bin/scala
Welcome to Scala 2.11.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_112).
Type in expressions for evaluation. Or try :help.

scala> @inline def foo(a: => Any) = if ("".isEmpty) a else ""
foo: (a: => Any)Any

scala> class InlineReturn { def test: Any = foo(return "") }
defined class InlineReturn

scala> :javap -c InlineReturn#test
  public java.lang.Object test();
    Code:
       0: new           #4                  // class java/lang/Object
       3: dup
       4: invokespecial #13                 // Method java/lang/Object."<init>":()V
       7: astore_1
       8: getstatic     #19                 // Field .MODULE$:L;
      11: new           #21                 // class InlineReturn$$anonfun$test$1
      14: dup
      15: aload_0
      16: aload_1
      17: invokespecial #24                 // Method InlineReturn$$anonfun$test$1."<init>":(LInlineReturn;Ljava/lang/Object;)V
      20: invokevirtual #28                 // Method .foo:(Lscala/Function0;)Ljava/lang/Object;
      23: goto          39
      26: astore_2
      27: aload_2
      28: invokevirtual #31                 // Method scala/runtime/NonLocalReturnControl.key:()Ljava/lang/Object;
      31: aload_1
      32: if_acmpne     40
      35: aload_2
      36: invokevirtual #34                 // Method scala/runtime/NonLocalReturnControl.value:()Ljava/lang/Object;
      39: areturn
      40: aload_2
      41: athrow
    Exception table:
       from    to  target type
           8    26    26   Class scala/runtime/NonLocalReturnControl

scala> :quit
```