[Stackmaps] Enable invoking the patchpoint intrinsic.

Patch by Kevin Modzelewski
Reviewers: atrick, ributzka
Reviewed By: ributzka
Subscribers: llvm-commits, reames

Differential Revision: http://reviews.llvm.org/D5634

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220055 91177308-0d34-0410-b5e6-96231b3b80d8