IR: Use the new DebugLoc API, NFC

Update lib/IR and lib/Bitcode to use the new `DebugLoc` API.  Added an
explicit conversion to `bool` (avoiding a conversion to `MDLocation`),
since a couple of these use cases need to handle broken code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233585 91177308-0d34-0410-b5e6-96231b3b80d8
10 files changed