Convert MEMBER_TYPE_FORCES_BLK to target hook

Convert MEMBER_TYPE_FORCES_BLK to target hook

	* stor-layout.c (compute_record_mode): Replace
	MEMBER_TYPE_FORCES_BLK with targetm.member_type_forces_blk.
	(layout_type): Likewise.

	* system.h: Poison MEMBER_TYPE_FORCES_BLK.

	* target.def (member_type_forces_blk): New target hook.

	* targhooks.c (default_member_type_forces_blk): New.
	* targhooks.h (default_member_type_forces_blk): Likewise.

	* doc/tm.texi.in (MEMBER_TYPE_FORCES_BLK): Removed.
	(TARGET_MEMBER_TYPE_FORCES_BLK): New hook.
	* doc/tm.texi: Regenerated.

	* config/ia64/hpux.h (MEMBER_TYPE_FORCES_BLK): Removed.

	* config/ia64/ia64.c (ia64_member_type_forces_blk): New
	function.
	(TARGET_MEMBER_TYPE_FORCES_BLK): New macro.

	* config/rs6000/rs6000.c (TARGET_MEMBER_TYPE_FORCES_BLK): New
	macro.
	(rs6000_member_type_forces_blk): New function.

	* config/rs6000/rs6000.h (MEMBER_TYPE_FORCES_BLK): Removed.

	* config/xtensa/xtensa.c (xtensa_member_type_forces_blk): New
	function.
	(TARGET_MEMBER_TYPE_FORCES_BLK): New macro.

	* config/xtensa/xtensa.h (MEMBER_TYPE_FORCES_BLK): Removed.

From-SVN: r190488