rs6000: Delete wg

rs6000: Delete wg

The "wg" constraint is used for the floating point side on mfpgpr
instructions.  Those instructions do not exist on any relevant
hardware.  This patch deletes the constraint and the insns using it.

	* config/rs6000/constraints.md (define_register_constraint "wg"):
	Delete.
	* config/rs6000/rs6000.h (enum r6000_reg_class_enum): Delete
	RS6000_CONSTRAINT_wg.
	* config/rs6000/rs6000.c (rs6000_debug_reg_global): Adjust.
	(rs6000_init_hard_regno_mode_ok): Adjust.
	* config/rs6000/rs6000.md (*mov<mode>_softfloat32, *movdi_internal64):
	Delete "wg" alternatives.
	* doc/md.texi (Machine Constraints): Adjust.

From-SVN: r271888