This PR migrates ZEND_INIT_FCALL opcodes to ZEND_INIT_FCALL_BY_NAME opcodes when copying the closure given to \parallel\run() or \parallel\Runtime::run() to the internal cache (in order to copy it to the thread it gets executed on). This is done because ZEND_INIT_FCALL is an optimised opcode for functions that are visible to the compiler at compile time and it does not do and runtime checks anymore and instead segfaults.

AFAIK this optimisation only triggers if the code looks something like this:

<?php
function foo() { return "OK"; }
$future = \parallel\run(function(){ 
    return foo(); 
});

This code is segfaulting (it won't if you \parallel\bootstrap("file_that_provides_foo_function.php");.
This PR make sure we do not segfault, but instead PHP raises a Fatal error: Call to undefined function foo() ... instead.

Fixes #317 for cases where OPcache is disabled