(INSTRUCTION_NULLIFIED): Allow specific targets to override.
* config/pa/tm-hppao.h (INSTRUCTION_NULLIFIED): Define to work
around losing mach kernel behavior.
(pc_in_interrupt_handler): New function. Also add PARAM decl.
(find_proc_framesize): Deal with HPUX setting SAVE_SP bit for
signal trampoline and interrupt routines.
(frame_saved_pc): Handle signal trampolines and interrupt routines.
(frame_chain, frame_chain_valid): Likewise.
(hppa_frame_find_saved_regs): Likewise. Also deal with special
saved regs convention for SP.
* tm-hppa[bho].h: FRAME_FIND_SAVED_PC_IN_SIGTRAMP): Define.
(FRAME_BASE_BEFORE_SIGTRAMP): Define.
(FRAME_FIND_SAVED_REGS_IN_SIGTRAMP): Define.
* tm-hppah.h (IN_SIGTRAMP): Define.