conversion of negative numbers to always result in -1.
While at it, rearrange the nearby comment so it fits in 80 chars per line,
like the rest of this file does.
PR: 107130
MFC after: 1 day
using these to load long doubles, but they aren't implemented in hardware
on (at least) UltraSPARC I and II machines.
Emulate popc in the user trap handler as well.
Re-arrange slightly to make support functions more accessible.
Reviewed by: tmm
