[Stackmaps] Fix the ID type to be i64 also for stackmaps (as we claim in the documenation)

The ID type for the stackmap and patchpoint intrinsics are in both cases i64.
This fixes an zero extend in the SelectionDAGBuilder that still used i32. This
also updates the target independent instructions STACKMAP and PATCHPOINT to use
the correct type.

llvm-svn: 201262