Add __glibc_unlikely hint in lll_trylock, lll_cond_trylock.

Add __glibc_unlikely hint in lll_trylock, lll_cond_trylock.

The macros lll_trylock, lll_cond_trylock are extended by an __glibc_unlikely
hint.  Now the trylock macros are based on the same assumption about a
free/busy lock as lll_lock.
With the hint gcc emits code in e.g. pthread_mutex_trylock which does
not use jumps if the lock is free.  Without the hint it had to jump away
if the lock is free.

Tested on s390x, ppc.

ChangeLog:

	* sysdeps/nptl/lowlevellock.h (lll_trylock, lll_cond_trylock):
	Add __glibc_unlikely hint.