S/390: Use define_subst for the setmem patterns.

S/390: Use define_subst for the setmem patterns.

While trying to get rid of the Y constraint in the setmem patterns I
noticed that for these patterns it isn't even a problem since these
always only use the constraint with a Pmode match_operand.  But while
being at it I've tried to fold some of the patterns a bit.

gcc/ChangeLog:

2016-03-01  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* config/s390/constraints.md ("jm8"): New constraint.
	* config/s390/predicates.md ("const_int_8bitset_operand"): New predicate.
	* config/s390/s390.md ("*setmem_long", "*setmem_long_and"): Merge
	into ...
	("*setmem_long<setmem_and>"): New pattern.
	("*setmem_long_31z", "*setmem_long_and_31z"): Merge
	into ...
	("*setmem_long_31z<setmem_and>"): New pattern.
	* config/s390/subst.md ("setmem_31z_subst", "setmem_and_subst"):
	New substitution rules with the required attributes.

From-SVN: r233848