This patch adds support for lock elision using ISA 2.07 hardware
transactional memory instructions for pthread_mutex primitives.
Similar to s390 version, the for elision logic defined in
'force-elision.h' is only enabled if ENABLE_LOCK_ELISION is defined.
Also, the lock elision code should be able to be built even with
a compiler that does not provide HTM support with builtins.
However I have noted the performance is sub-optimal due scheduling
pressures.
Commit 887865f remove the lll_robust_trylock definition on all
architectures, however for powerpc both __lll_trylock and
__lll_cond_trylock were based on lll_robust_trylock definition.
This patch restore it with a different name.
