* arm-tdep.c: Include "observer.h".

	* arm-tdep.c: Include "observer.h".
	(arm_prologue_this_id): Use frame PC if get_frame_func returns 0.
	(arm_exidx_data_key): New static variable.
	(struct arm_exidx_entry, arm_exidx_entry_s): New data types.
	(struct arm_exidx_data): Likewise.
	(arm_exidx_data_free): New function.
	(arm_compare_exidx_entries): Likewise.
	(arm_obj_section_from_vma): Likewise.
	(arm_exidx_new_objfile): Likewise.
	(arm_find_exidx_entry): Likewise.
	(arm_exidx_fill_cache): Likewise.
	(arm_exidx_unwind_sniffer): Likewise.
	(arm_exidx_unwind): New global variable.
	(arm_gdbarch_init): Append unwinder arm_exidx_unwind.
	(_initialize_arm_tdep): Attach arm_exidx_new_objfile to new_objfile
	observer.  Register arm_exidx_data_key as objfile data.