Implement hwasan target_hook.

Implement hwasan target_hook.

gcc/ChangeLog:

	* doc/invoke.texi (x86 options): Document
	-mlam={none,u48,u57}.
	* config/i386/i386-opts.h (enum lam_type): New enum.
	* config/i386/i386.cc (ix86_memtag_can_tag_addresses): New.
	(ix86_memtag_set_tag): Ditto.
	(ix86_memtag_extract_tag): Ditto.
	(ix86_memtag_add_tag): Ditto.
	(ix86_memtag_tag_size): Ditto.
	(ix86_memtag_untagged_pointer): Ditto.
	(TARGET_MEMTAG_CAN_TAG_ADDRESSES): New.
	(TARGET_MEMTAG_ADD_TAG): Ditto.
	(TARGET_MEMTAG_SET_TAG): Ditto.
	(TARGET_MEMTAG_EXTRACT_TAG): Ditto.
	(TARGET_MEMTAG_UNTAGGED_POINTER): Ditto.
	(TARGET_MEMTAG_TAG_SIZE): Ditto.
	(IX86_HWASAN_SHIFT): Ditto.
	(IX86_HWASAN_TAG_SIZE): Ditto.
	* config/i386/i386-expand.cc (ix86_expand_call): Untag code
	pointer.
	* config/i386/i386-options.cc (ix86_option_override_internal):
	Error when enable -mlam=[u48|u57] for 32-bit code.
	* config/i386/i386.opt: Add -mlam=[none|u48|u57].
	* config/i386/i386-protos.h (ix86_memtag_untagged_pointer):
	Declare.
	(ix86_memtag_can_tag_addresses): Ditto.