re PR target/11848 ([darwin] [no support for 128 doubles] internal compiler error for -mlong-double-128)

	PR target/11848
	* rs6000.h (CANNOT_CHANGE_MODE_CLASS): Allow change of mode
	in floating-point registers between TFmode and DImode.
	* rs6000.c (rs6000_emit_move): Split moves early.
	(secondary_reload_class): Random Whitespace Change.
	(rs6000_split_multireg_move): Support moves involving FP registers.
	Emit instructions directly.
	* rs6000-protos.h (rs6000_split_multireg_move): Update prototype.
	* altivec.md: Update for changes to rs6000_split_multireg_move.
	* rs6000.md: Update for changes to rs6000_split_multireg_move.
	(movtf_internal): Support moves to/from GPRs.

From-SVN: r74454