unwind-dw2-xtensa.h (_Unwind_FrameState): Remove pc field and add signal_ra.

	* config/xtensa/unwind-dw2-xtensa.h (_Unwind_FrameState): Remove pc
	field and add signal_ra.
	* config/xtensa/unwind-dw2-xtensa.c (uw_frame_state_for): Remove
	assignments to frame state pc.  Move end of stack check after
	MD_FALLBACK_FRAME_STATE_FOR.
	(uw_update_context_1): Use frame state signal_regs if set, instead
	of checking signal_frame flag.
	(uw_update_context): Use frame state signal_ra if set.
	* config/xtensa/linux.h (MD_UNWIND_SUPPORT): Define.
	* config/xtensa/linux-unwind.h: New file.

From-SVN: r131622