Log Message:
mpg123: update to 1.26.5 and use default optimization

This approaches a serious performance issue with 1.26.x when
resampling is used on certain platforms (observed on SPARC).
Floating point denormals crop up. This change approaches that
two-fold

1. Do not disable default optimization flags for GCC.
2. Update to 1.26.5 that contains code to avoid denormals.

The default flags are about code optimization (like -ffast-math),
not the target architecture, so should not affect portability.
They are also rather safe and tested as development of mpg123
always has them in place. This is how it is meant to be played;-)

Approved during freeze by wiz.