DebugInfo: Simplify/clarify propagation of typemembers between declaration and definition

Based on code review feedback from Eric Christopher (on r188739) and
Adrian Prantl (r188642).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188829 91177308-0d34-0410-b5e6-96231b3b80d8
Look at lowercase version of argv[0] when determining driver mode

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188833 91177308-0d34-0410-b5e6-96231b3b80d8
DebugInfo: comment/inlining based on feedback from Eric & Adrian

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188834 91177308-0d34-0410-b5e6-96231b3b80d8