Port some "pxfmt" changes that didn't come over already.

Not sure why Git didn't pull these over, but it didn't, and so I am manually
porting these changes.
Eliminate "pxfmt" compiler warnings on Linux.

The compiler noticed that 2 members of the small_fp<nbits> struct weren't being
used.  Sure enough, so I removed them.
Merge pull request #65 from IanAtLunarG/pxfmt_140514a

Eliminate warnings on Linux & port some other changes...