Add --suppress-backtrace=num option to limit the backtrace length - #3047

```
$ ./miniruby --backtrace-limit=5 -e 'def f1 = raise
def f2 = f1
def f3 = f2
def f4 = f3
def f5 = f4
def f6 = f5
def f7 = f6
def f8 = f7
def f9 = f8
f9
'
-e:1:in `f1': unhandled exception
	from -e:2:in `f2'
	from -e:3:in `f3'
	from -e:4:in `f4'
	from -e:5:in `f5'
	from -e:6:in `f6'
	 ... 5 levels...
```

[Feature ruby#8661]