When merging functions across modules (and in particular, instantiations of
member functions), ensure that the redecl chain never transitions from 'inline'
to 'not inline', since that violates an AST invariant.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@209794 91177308-0d34-0410-b5e6-96231b3b80d8