Added the '++' and '--' prefix unary operators to return the incremented or decremented value of an object, without modifying the original object.

Example:
	var x = 41;
	say ++x;	# prints: 42
	say x;		# prints: 41

NOTE: It doesn't work like the postfix '++'!

Example:
	var x = 41;
	say x++;	# prints: 42
	say x;		# prints: 42