S/390: Emit vector alignment hints for z13 if AS accepts them

S/390: Emit vector alignment hints for z13 if AS accepts them

Since 87cb9423add vector alignment hints are emitted for target z13,
too.  This patch changes this behaviour in the sense that alignment
hints are only emitted for target z13 if the assembler accepts them.

gcc/ChangeLog:

	* config.in: Regenerate.
	* config/s390/s390.c (print_operand): Emit vector alignment hints
	for target z13, if AS accepts them.  For other targets the logic
	stays the same.
	* config/s390/s390.h (TARGET_VECTOR_LOADSTORE_ALIGNMENT_HINTS): Define
	macro.
	* configure: Regenerate.
	* configure.ac: Check HAVE_AS_VECTOR_LOADSTORE_ALIGNMENT_HINTS_ON_Z13.