DebugInfo: Fix inlining with #file directives a little harder

Seems my previous fix was insufficient - we were still not adding the
inlined function to the abstract scope list. Which meant it wasn't
flagged as inline, didn't have nested lexical scopes in the abstract
definition, and didn't have abstract variables - so the inlined variable
didn't reference an abstract variable, instead being described
completely inline.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209602 91177308-0d34-0410-b5e6-96231b3b80d8