Intrinsics: introduce llvm_any_ty aka ValueType Any

Specifically, gc.result benefits from this greatly. Instead of:

gc.result.int.*
gc.result.float.*
gc.result.ptr.*
...

We now have a gc.result.* that can specialize to literally any type.

Differential Revision: http://reviews.llvm.org/D7020

llvm-svn: 226857