read-rtl.c (read_rtx): Allow 's' and 'T' strings to be omitted, treating missing ones as "".

	* read-rtl.c (read_rtx): Allow 's' and 'T' strings to be omitted,
	treating missing ones as "".
	* config/mips/mips.md: Remove constraints from match_operands and
	match_scratches if they appear in define_expands (except reload*),
	define_peephole2s, define_splits or attribute specifications.
	* config/mips/7000.md, config/mips/sb1.md: Remove match_operand
	constraint strings.

From-SVN: r81676