Clang changes for overloading invariant.start and end intrinsics

This change depends on the corresponding LLVM change at:
https://reviews.llvm.org/D22519

The llvm.invariant.start and llvm.invariant.end intrinsics currently
support specifying invariant memory objects only in the default address
space.

With this LLVM change, these intrinsics are overloaded for any adddress space
for memory objects and we can use these llvm invariant intrinsics in
non-default address spaces.

Example: llvm.invariant.start.p1i8(i64 4, i8 addrspace(1)* %ptr)

This overloaded intrinsic is needed for representing final or invariant
memory in managed languages.

llvm-svn: 276448