standards/59797: Implement C99's round[f]() math fucntions

[Steven G. Kargl]

David Schultz wrote:
> 
> BTW, benchmarking shows that using the sample implementation that
> appears in the C99 standard results in a slowdown of two orders of
> magnitude over your round() implementation and four orders of
> magnitude over the x87 frndint instruction.  Just setting the
> rounding mode and calling rint() also results in a significant
> slowdown.  Thus, we definitely want something that's in the spirit
> of what you wrote, but perhaps one that operates on the bits directly.
> 

I looked at the glibc implementation of round().  It does
bit twiddling, but I would definitely recommend not using
the glibc version because of licensing and possible copyright
infringement concerns [hiint compare glibc's round() with
fdlibm's ceil()].  

-- 
Steve
http://troutmask.apl.washington.edu/~kargl/