[ADT] Switch to indirect even the trivial case through an object pointer

that has required alignment. This avoids issues that keep coming up with
function pointers being less aligned.

I'm pretty annoyed that we can't take advantage of function alignment
even on platforms where they *are* aligned, but build modes and other
things make taking advantage of it somewhere between hard and
impossible. The best case scenario would still embed various build modes
into the ABI causing really hard to debug issues if you compiled one
object file differently from another. =/

This should at least bring the bots back that were having trouble with
this.

llvm-svn: 336337