[msan] Add compile-time checks for missing origins.

This change makes MemorySanitizer instrumentation a bit more strict
about instructions that have no origin id assigned to them.

This would have caught the bug that was fixed in r222918.

No functional change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222997 91177308-0d34-0410-b5e6-96231b3b80d8