Don't test for zero backchain pointer to recognize a signal
handler frame, if read() gets interrupted by a signal, the
backchain will be non zero.
(SIG_FRAME_FP_OFFSET): Move to here from rs6000-tdep.c,
improve comment.
(SIG_FRAME_PC_OFFSET): New definition.
(FRAME_SAVED_PC): Return saved pc from sigcontext if this
is a signal handler frame.
* rs6000-tdep.c (function_frame_info): Do not error out
if we can't access the instructions.
* config/rs6000/tm-rs6000.h (CONVERT_FROM_FUNC_PTR_ADDR):
New definition to get the function address from a function pointer.
* valops.c (find_function_addr): Use it when calling a user
function through a function pointer.
config/gould/tmp-{pn,np1}.h,
config/{sparc/tm-sparc.h,pyr/tm-pyr.h,vax/tm-vax.h}: Remove field
next_frame from struct frame_info. It has no purpose beyond
->next->frame and is an artifact from GDB 2.8.
config files moved to an appropriate config/<cpu> subdirectory.
* nm-*, xm-*, tm-*: All native, host, and target files, which
get linked to nm.h, xm.h, and tm.h respectively by configure,
moved to appropriate config/<cpu> subdirectory.
