Simplify loop code-gen on Moar.
Simplify loop code-gen on Moar.

Don't need to keep result type of block at this level; it's not what
NQP nor Rakudo need. Means we can convey more void context.

cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp