arm, aarch64: Add support for __GCC_ASM_FLAG_OUTPUTS__

arm, aarch64: Add support for __GCC_ASM_FLAG_OUTPUTS__

Since all but a couple of lines is shared between the two targets,
enable them both at once.

	* config/arm/aarch-common-protos.h (arm_md_asm_adjust): Declare.
	* config/arm/aarch-common.c (arm_md_asm_adjust): New.
	* config/arm/arm-c.c (arm_cpu_builtins): Define
	__GCC_ASM_FLAG_OUTPUTS__.
	* config/arm/arm.c (TARGET_MD_ASM_ADJUST): New.
	* config/aarch64/aarch64-c.c (aarch64_define_unconditional_macros):
	Define __GCC_ASM_FLAG_OUTPUTS__.
	* config/aarch64/aarch64.c (TARGET_MD_ASM_ADJUST): New.
	* doc/extend.texi (FlagOutputOperands): Add documentation
	for ARM and AArch64.

From-SVN: r278226