builtin_return_addr vs frame_pointer_needed vs -O3

[DJ Delorie]

It does fix 20010122-1, though :-)

> 	* config/i386/i386.c (ix86_frame_pointer_required): New.
> 	(ix86_setup_frame_addresses): New.
> 	(struct machine_funciton): Add accesses_prev_frame.
> 	* config/i386/i386.h (FRAME_POINTER_REQUIRED): Call
> 	ix86_frame_pointer_required.
> 	(SUBTARGET_FRAME_POINTER_REQUIRED): New.
> 	(SETUP_FRAME_ADDRESSES): New.
> 	* config/i386/i386-protos.h: Update.
> 	* config/i386/sco5.h (SUBTARGET_FRAME_POINTER_REQUIRED): Rename
> 	from FRAME_POINTER_REQUIRED.
> 	* config/i386/svr3gas.h: Likewise.
> 	* config/i386/sysv3.h: Likewise.
> 	* config/i386/v3gas.h: Likewise.