FEAT: [IA-32] Simple exception handling for Red/System.

Use THROW <integer!> to raise an exception and send back an integer ID. Use [catch] attribut in function's spec block where you want to process the exception. Use system/thrown to read the caught exception ID.

Example:

	foo: func [[catch]][
		print "2"
		throw 10
		print "KO"
	]

	print "1"
	foo
	print "3"
	print ["^/thrown value: " system/thrown lf]

will output:
	123
	thrown value: 10
FIX: issue #465 (make string! 0 and appending char! values produces incorrect results)
FIX: [IA-32] now the catch flag is discarded using EDI register instead of EDX (to avoid possible corruption on 64-bit values returned by functions).
FIX: comments fixing.
FEAT: [ARM] added support for exceptions.
FEAT: [IA-32] enhanced exception implementation, now [catch] attribute will resume execution at same level. ARM upgrade is pending.
FEAT: added support for EXIT and RETURN to the interpreter.
FEAT: removed internal placeholders for EXIT and RETURN. Now they are pure dialect keywords.
FEAT: [ARM] upgraded exceptions support to new behavior.
FIX: [ARM] storing 64-bit floats was broken (high part was corrupted on writing).
FIX: exceptions root barrier aligned to 64-bit, and FP repositioned just after catch flag.
Added comment mode to count-delimiters func.
Entabbed file.