Remove some bogus type constraints.

Since we typically calculate with floats in NQP, we can't rely on the
arguments being int here. Somehow we get away with this on Parrot, but
NQP JVM enforces them more Perl 6-ishly. Also, they may have led to
reboxing, so we may be better off without them anyway.
Remove misleading commented out code and a hack.

The code explained what the C op it was replaced with at the point it
was translated. However, now things have evolved, so better to just
toss it.