* read-rtl.c (struct macro_traverse_data): Define.
	(map_attr_string): New static function, broken out of
	apply_macro_to_string.
	(mode_attr_index, apply_mode_maps): New static functions.
	(apply_macro_to_string): Call map_attr_string.
	(apply_macro_to_rtx): Add mode_maps and infile parameters.  Change
	all callers.
	(apply_macro_traverse): Expect data to point to a struct
	macro_traverse_data.
	(read_rtx): Add mode_maps local variable.  Use mode_traverse_data
	to pass data through htab_traverse.
	(read_rtx_1): Add mode_maps parameter.  Change all callers.
	Handle mode names which are attribute strings.
	* doc/md.texi (Substitutions): Rename from String Substitutions.
	Change references.  Document using attributes as modes.

From-SVN: r99548