re PR rtl-optimization/13169 (asm using r30 or r31 confuses global_alloc)

	PR 13169
	* basic-block.h (PROP_ASM_SCAN): Define.
	* final.c (regs_asm_clobbered): New array.
	* regs.h (regs_asm_clobbered): Declare.
	* flow.c (life_analysis): Init it.
	(mark_set_regs): Set PROP_ASM_SCAN for asms.
	(mark_set_1): Set regs_asm_clobbered.
	* global.c (global_alloc): Don't set eliminable_regset when
	regs_asm_clobbered.

From-SVN: r74363