Remove support for labels as immediate children of IF/ELSE/WHILE/FOR/DO.

This extremely uncommon coding pattern was becoming a hell to support. It has caused many bugs in past that need them being treated as special cases.

Getting rid of the possibility entirely seems like the best approach.

It's still supported if the code is not to be optimized (e.g. with --pretty).

lslopt/lslfoldconst.py

@@ -24,6 +24,7 @@ from lslfuncs import ZERO_VECTOR, ZERO_ROTATION
 import math
 from lslfuncopt import OptimizeFunc, OptimizeArgs, FuncOptSetup
 
+# TODO: Remove special handling of @ within IF,WHILE,FOR,DO
 
 class foldconst(object):