Debug Info: use createAndAddDIE to wrap around "new DIE" in DwarfDebug.

This commit ensures DIEs are constructed within a compile unit and
immediately added to their parents.

Reviewed off-list by Eric.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193568 91177308-0d34-0410-b5e6-96231b3b80d8