* amd64-nat.h (amd64_native_gregset_supplies_p): Add gdbarch as
	parameter.
	* amd64-nat.c (amd64_native_gregset_supplies_p): Likewise.

	(amd64_native_gregset_reg_offset): Add gdbarch as parameter. Replace
	current_gdbarch by gdbarch. Update caller.

	* amd64-linux-nat.c (amd64_linux_fetch_inferior_registers)
	(amd64_linux_store_inferior_registers): Use get_regcache_arch to get at
	the current architecture. Update calls of
	amd64_native_gregset_supplies_p.
	* amd64bsd-nat.c (amd64bsd_fetch_inferior_registers)
	(amd64bsd_store_inferior_registers): Likewise.