* reload.c (find_reloads): Handle constraint letters marked by
	EXTRA_ADDRESS_CONSTRAINT and EXTRA_MEMORY_CONSTRAINT.
	(alternative_allows_memconst): Likewise.
	* reload1.c (maybe_fix_stack_asms): Likewise.
	* recog.c (asm_operand_ok, preprocess_constraints,
	constrain_operands): Likewise.
	* regclass.c (record_operand_costs, record_reg_classes): Likewise.
	* local-alloc.c (block_alloc, requires_inout): Likewise.
	* stmt.c (parse_output_constraint, parse_input_constraint): Likewise.

	* defaults.h (EXTRA_MEMORY_CONSTRAINT): Provide a default.
	(EXTRA_ADDRESS_CONSTRAINT): Likewise.
	* doc/tm.texi: Document these two new target macros.

	* config/s390/s390.c (s390_expand_plus_operand): Accept already
	valid operands.
	(q_constraint): New function.
	config/s390/s390-protos.h (q_constraint): Declare it.
	config/s390/s390.h (EXTRA_CONSTRAINT): Use it.
	(EXTRA_MEMORY_CONSTRAINT): New macro.

	* config/s390/s390.md: Throughout the machine description,
	replace all instances of the constraint combinations 'Qo'
	or 'oQ' with simply 'Q'.

From-SVN: r56291