Replace CpuSSE3 with CpuCX16 for cmpxchg16b

Replace CpuSSE3 with CpuCX16 for cmpxchg16b

gas/

	* config/tc-i386.c (cpu_arch): Add .cx16.
	* doc/c-i386.texi: Document .cx16.

gas/testsuite/

	* gas/i386/x86-64-arch-2.s: Add test for cmpxchg16b.
	* gas/i386/x86-64-arch-2.d: Update correspondingly.
	* gas/i386/x86-64-arch-2-bdver2.d: Likewise.
	* gas/i386/x86-64-arch-2-btver1.d: Likewise.
	* gas/i386/x86-64-arch-2-btver2.d: Likewise.
	* gas/i386/x86-64-arch-2-lzcnt.d: Likewise.
	* gas/i386/x86-64-arch-2-prefetchw.d: Likewise.
	* gas/i386/ilp32/x86-64-arch-2.d: Likewise.

opcodes/

	* i386-gen.c (cpu_flag_init): Add CpuCX16 to CPU_NOCONA_FLAGS,
	CPU_CORE_FLAGS, CPU_CORE2_FLAGS, CPU_COREI7_FLAGS,
	CPU_BDVER1_FLAGS, CPU_BDVER2_FLAGS, CPU_BTVER1_FLAGS,
	CPU_BTVER2_FLAGS.  Add CPU_CX16_FLAGS.
	(cpu_flags): Add CpuCX16.
	* i386-opc.h (CpuCX16): New.
	(i386_cpu_flags): Add cpucx16.
	* i386-opc.tbl: Replace CpuSSE3 with CpuCX16 for cmpxchg16b.
	* i386-tbl.h: Regenerate.
	* i386-init.h: Likewise.