* amd64-tdep.c (amd64_return_value): Use `gdb_byte *' in casts.

(amd64_push_arguments): Use gdb_byte instead of bfd_byte.  Use
gdb_byte for buf.
(amd64_push_dummy_call): Use gdb_byte for buf.
(amd64_analyze_prologue): Use gdb_byte for proto, buf and op.
(amd64_frame_cache, amd64_sigtramp_frame_cache)
(amd64_unwind_dummy_id): Use gdb_byte for buf.
(amd64_supply_fxsave, amd64_collect_fxsave): Use `gdb_byte *' for
regs.
* amd64obsd-tdep.c (amd64obsd_supply_regset): Use `gdb_byte *' in
casts.
(amd64obsd_sigtramp_p): Use gdb_byte for sigreturn and `gdb_byte
*' for buf,