Fix line numbers for code inlined from __nodebug__ functions.

Instructions from __nodebug__ functions don't have file:line
information even when inlined into no-nodebug functions. As a result,
intrinsics (SSE and other) from <*intrin.h> clang headers _never_
have file:line information.

With this change, an instruction without !dbg metadata gets one from
the call instruction when inlined.

Fixes PR19001.