* inferior.h (ARCH_NUM_REGS): New macro, actual number of
registers in use by the inferior.
* coredep.c (fetch_core_registers, register_addr): Use it.
* findvar.c (registers_changed, registers_fetched,
read_register_bytes): Ditto.
* infcmd.c (do_registers_info, registers_info): Ditto.
* infptrace.c (fetch_inferior_registers,
store_inferior_registers): Ditto.
* stack.c (frame_info): Ditto.
* coredep.c (CORE_REGISTER_ADDR): New macro.
(fetch_core_registers): Use it.