Moved back to the standard library without loop primitives, and instead introduce a intrinsification for the #whileTrue: and #whileFalse: messages.

This also introduces more general rewriting.
All message nodes start out uninitialized, and will specialize based on a few criteria, currently only to #whileTrue: or #whileFalse:

Signed-off-by: Stefan Marr <git@stefan-marr.de>