Add a fast/emulated gettimeofday called sphgtod.

The include file sphgtod.h provides a prototype for sphgtod, which copies
the prototype for gettimeofday.  This implementation is provided in a
static-only library called libsphgtod.a.

This emulated gettimeofday will perform best on Power7, in 64-bit.  The
32-bit version is not yet optimized and may perform worse than the 32-bit
version of gettimeofday.
Cleanup trailing whitespace.