arm.md (thumb1_addsi3): Add alternative and split for computing the sum of the...

arm.md (thumb1_addsi3): Add alternative and split for computing the sum of the stack pointer and a...

	* config/arm/arm.md (thumb1_addsi3): Add alternative and split for
	computing the sum of the stack pointer and a large constant.
	* config/arm/constraints.md (M): Remove superfluous parentheses.
	(Pc): New constraint.

From-SVN: r162355