* config/obj-som.h (obj_attach_unwind_info): Define as a hook

	* config/obj-som.h (obj_attach_unwind_info): Define as a hook
	so GAS can attach unwind descriptor information to a BFD symbol.
	* config/tc-hppa.c (fix_new_hppa): If necessary attach unwind
	descriptor information to the BFD symbol.
	(md_apply_fix): R_HPPA_ENTRY and R_HPPA_EXIT can never be "applied",
	they are simply markers.  Make R_HPPA_UNWIND_* handling OBJ_ELF
	dependent.
	(pa_build_unwind_subspace): Whole function is OBJ_ELF dependent.
	(pa_entry): Build a R_HPPA_ENTRY relocation when configured for SOM.
	(pa_exit): Likewise, but built a R_HPPA_EXIT relocation.  Do not
	build "end-of-function" symbols for SOM, they are not needed.