Update i386 and amd64 ports for unwinder changes.

	* amd64-tdep.c (amd64_frame_cache): Expect this_frame.
	(amd64_frame_this_id, amd64_frame_prev_register): Update signature.
	(amd64_frame_unwind): Use default_frame_sniffer.
	(amd64_frame_sniffer): Delete.
	(amd64_sigtramp_frame_cache): Expect this_frame.
	(amd64_sigtramp_frame_this_id, amd64_sigtramp_frame_prev_register)
	(amd64_sigtramp_frame_sniffer): Update signature.
	(amd64_sigtramp_frame_unwind): Add amd64_sigtramp_frame_sniffer.
	(amd64_frame_base_address): Expect this_frame.
	(amd64_dummy_id): Renamed from amd64_unwind_dummy_id.  Expect
	this_frame.
	(amd64_init_abi): Use set_gdbarch_dummy_id and
	frame_unwind_append_unwinder.
	* i386-tdep.c (i386_frame_cache): Expect this_frame.
	(i386_frame_this_id, i386_frame_prev_register): Update signature.
	(i386_frame_unwind): Use default_frame_sniffer.
	(i386_frame_sniffer): Delete.
	(i386_sigtramp_frame_cache): Expect this_frame.
	(i386_sigtramp_frame_this_id, i386_sigtramp_frame_prev_register)
	(i386_sigtramp_frame_sniffer): Update signature.
	(i386_sigtramp_frame_unwind): Use i386_sigtramp_frame_sniffer.
	(i386_frame_base_address): Update signature.
	(i386_dummy_id): Rename from i386_unwind_dummy_id.  Expect this_frame.
	(i386_push_dummy_call): Update comment.
	(i386_sigtramp_p, i386_svr4_sigtramp_p, i386_svr4_sigcontext_addr):
	Expect this_frame.
	(i386_gdbarch_init): Use set_gdbarch_dummy_id, dwarf2_append_unwinders,
	and frame_unwind_append_unwinder.
	* amd64-linux-tdep.c, amd64-sol2-tdep.c, amd64fbsd-tdep.c,
	amd64nbsd-tdep.c, amd64obsd-tdep.c, i386-linux-tdep.c,
	i386-nto-tdep.c, i386bsd-tdep.c, i386-sol2-tdep.c, i386obsd-tdep.c,
	i386nbsd-tdep.c: Update for unwinder changes.