Change -O options of release libraries

This patch changes the -O option used on release libraries. It seems that the
GCC compiler isn't obeying the memory barriers for ordered instruction accesses
when this option is set to anything else than 0. This leads to all sorts of
problems on the atomic POWER CAS embedded assembler instructions.
General fixes to POWER CAS atomic routines

This patch ported the big-endian (BE) version of the POWER CAS assembly
routines, as well as fixes for some errors found on the little-endian (LE)
ones, basically by calling the internal GCC macros directly (and not relying
on Intel TBB to do so). This seems to fix some of the random errors found on
previous LE test executions. This also provides some syntax cleanup on the
power specific file and atomic.h.