Add check for invalid register in AVX512 gathers

Add check for invalid register in AVX512 gathers

AVX512 gather instructions shouldn't accept the same register for both
destination and index.

gas/

2014-01-22  Michael Zolotukhin  <michael.v.zolotukhin@gmail.com>

	PR gas/16489
	* config/tc-i386.c (check_VecOperands): Add check for invalid
	register set in AVX512 gathers.

gas/testsuite/

2014-01-22  Michael Zolotukhin  <michael.v.zolotukhin@gmail.com>

	PR gas/16489
	* gas/i386/vgather-check.s: Add tests for AVX512 gathers.
	* gas/i386/x86-64-vgather-check.s: Likewise.
	* gas/i386/vgather-check-error.l: Update correspondingly.
	* gas/i386/vgather-check-none.d: Likewise.
	* gas/i386/vgather-check-warn.d: Likewise.
	* gas/i386/vgather-check-warn.e: Likewise.
	* gas/i386/vgather-check.d: Likewise.
	* gas/i386/x86-64-vgather-check-error.l: Likewise.
	* gas/i386/x86-64-vgather-check-none.d: Likewise.
	* gas/i386/x86-64-vgather-check-warn.d: Likewise.
	* gas/i386/x86-64-vgather-check-warn.e: Likewise.
	* gas/i386/x86-64-vgather-check.d: Likewise.