* frame.c (generic_unwind_get_saved_register): Make non-static.

	* frame.c (generic_unwind_get_saved_register): Make non-static.
	* frame.h (generic_unwind_get_saved_register): Declare.
	* mips-tdep.c (read_next_frame_reg): Fetch register from
	current regcache when frame is NULL.
	(mips_init_extra_frame_info): Pass NULL explicitly for parameter
	that must be NULL.
	(mips_get_saved_register): Call generic_unwind_get_saved_register()
	instead of frame_register_unwind().