x86: Support x86 Zhaoxin PadLock XMODX instructions

x86: Support x86 Zhaoxin PadLock XMODX instructions

The CPUID EDX bit[28] indicates its enablement, and it includes REP
XMODEXP and REP MONTMUL2. XMODX stands for modular exponentiation, it indicates
the support of modular exponentiation feature, both REP XMODEXP and
REP MONTMUL2 use it.

gas/ChangeLog:

	* NEWS: Support Zhaoxin PadLock XMODX instructions.
	* config/tc-i386.c (add_branch_prefix_frag_p): Don't add prefix to
	PadLockXMODX instructions.
	(output_insn): Handle PadLockXMODX instructions.
	* doc/c-i386.texi: Document PadLockXMODX.
	* testsuite/gas/i386/i386.exp: Add PadLockXMODX test.
	* testsuite/gas/i386/padlockxmodx.d: Ditto.
	* testsuite/gas/i386/padlockxmodx.s: Ditto.

opcodes/ChangeLog:

	* i386-dis.c: Add PadLockXMODX.
	* i386-gen.c: Ditto
	* i386-opc.h (CpuPadLockXMODX): New.
	* i386-opc.tbl: Add Zhaoxin PadLock XMODX instructions.
	* i386-tbl.h: Regenerated.
	* i386-mnem.h: Ditto.
	* i386-init.h: Ditto.