If two sibling modules declare the same entity, and we indirectly pull a
declaration of that entity in from one of those modules, keep track of the fact
that we've not completed the redeclaration chain yet so that we can pull the
remaining declarations in from the other module if they're needed.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@209161 91177308-0d34-0410-b5e6-96231b3b80d8