Re-add hack that caused regression.

This fixes llvm.org/PR15350.

Before:
Constructor(int Parameter = 0)
    : aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(aaaaaaaaaaaaaaaaa),
                aaaaaaaaaaaa(aaaaaaaaaaaaaaaaa) {}

After:
Constructor(int Parameter = 0)
    : aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(aaaaaaaaaaaaaaaaa),
      aaaaaaaaaaaa(aaaaaaaaaaaaaaaaa) {}

I think the correct solution is to put the VariablePos into
ParenState, not LineState. Added FIXME.