PowerPC: Add the low level infrastructure for pthreads lock elision

This patch adds support for lock elision using ISA 2.07 hardware
transactional memory instructions.
Skip checks in pthread_mutex_destroy when doing elision

When doing elisison the __nusers field is not updated, thus can have an
arbitrary value.

	[BZ #16657]
	* nptl/pthread_mutex_destroy.c (__pthread_mutex_destroy): Skip
	checks when doing elision.
	* nptl/sysdeps/unix/sysv/linux/x86/pthread_mutex_destroy.c: New
	* file.
PowerPC: Adjusting LE mutex destroy

This patch adjust the pthread_mutex_t destroy to take acocunt of lock
elision.
PowerPC: Add adaptive elision to rwlocks

This patch adds support for lock elision using ISA 2.07 hardware
transactional memory for rwlocks.
PowerPC: abort transaction in syscalls

Linux kernel powerpc documentation states issuing a syscall inside a
transaction is not recommended and may lead to undefined behavior. It
also states syscalls does not abort transactoin neither they run in
transactional state.

To avoid side-effects being visible outside transactions, GLIBC with lock
elision enable issues a transaction abort instruction just before all
syscalls if hardware supports hardware transactions.