invoke.texi (-mcpu=power8): Document.

invoke.texi (-mcpu=power8): Document.

	* doc/invoke.texi (-mcpu=power8): Document.
	* config.in (HAVE_AS_POWER8): New.
	* config.gcc: Add cpu_type power8.
	* configure.ac: (HAVE_AS_POWER8): Check for assembler support for
	the POWER8 instructions.
	* configure: Regenerate.
	* config/rs6000/rs6000.h: (ASM_CPU_POWER8_SPEC): Define.
	(ASM_CPU_SPEC): Pass %(asm_cpu_power8) for -mcpu=power8.
	(EXTRA_SPECS): Add asm_cpu_power8 spec string.
	* config/rs6000/rs6000-cpus.def (processor_target_table): Alias
	POWER8 to POWER7.
	* config/rs6000/rs6000-tables.opt: Regenerate.
	* config/rs6000/driver-rs6000.c (ASM_CPU_SPEC): For -mcpu=power8,
	pass %(asm_cpu_power8)/-mpwr8.
	* config/rs6000/aix53.h: Likewise.
	* config/rs6000/aix61.h: Likewise.

From-SVN: r193307