* Use bit twiddling. This requires inclusion of math_private.h
and inclusion of float.h in s_roundl.c. Raise invalid exception.
* Use literal integer constants where possible. Let the compiler
do the appropriate conversion.
* In s_roundf.c, use an F suffix on float constants instead of
promoting float to double and then converting the result back
to float. In s_roundl.c, use an L suffix.
* In s_roundl.c, use the ENTERI and RETURNI macros. This requires
the inclusion of fpmath.h and on __i386__ class hardware ieeefp.h.
Reviewed by: bde
db89cf8efb