x86: Use RTM intrinsics in pthread mutex lock elision

Since RTM intrinsics are supported in GCC 4.9, we can use them in
pthread mutex lock elision.

	* sysdeps/unix/sysv/linux/x86/Makefile (CFLAGS-elision-lock.c):
	Add -mrtm.
	(CFLAGS-elision-unlock.c): Likewise.
	(CFLAGS-elision-timed.c): Likewise.
	(CFLAGS-elision-trylock.c): Likewise.
	* sysdeps/unix/sysv/linux/x86/hle.h: Rewritten.