This is an almost-final step in eliminating debug-intrinsics -- read more
about that here: https://llvm.org/docs/RemoveDIsDebugInfo.html . To
correctly update variable location information in the background when
inserting instructions, we need some information carried at runtime in
BasicBlock::iterator, hence deprecating pointer-insertion.
An immediate fix for any deprecation warnings is to call "getIterator"
on the insertion position pointer. If you intend on inserting at the start
of a block, use BB->begin() or similar methods to fetch the appropriate
iterator.