Do not call replaceAllUsesWith to upgrade calls to ARC runtime functions

Do not call replaceAllUsesWith to upgrade calls to ARC runtime functions
to intrinsic calls

This fixes a bug in r368311.

It turns out that the ARC runtime functions in the IR can have pointer
parameter types that are not i8* or i8**. Instead of RAUWing normal
functions with intrinsics, manually bitcast the arguments before passing
them to the intrinsic functions and bitcast the return value back to the
type of the original call instruction.

This recommits r368634, which was reverted in r368637. The loop in the
patch was iterating over uses of a function and deleting function calls
inside it, which caused bots to crash.

rdar://problem/54125406

Differential Revision: https://reviews.llvm.org/D66047

llvm-svn: 368646