* emit-rtl.c (gen_lowpart_common): Use simplify_gen_subreg
	for constants.
	(constant_subword): Delete.
	* rtl.h (constant_subword): Delete prototype.
	(immed_double_const): Is not in varasm.c.
	* simplify-rtx.c (simplify_immed_subreg): New.
	(simplify_subreg): Use simplify_immed_subreg.

From-SVN: r75487