clang-format: Fix incorrect detection of QT-signals access specifier.

Before:
  void f() {
  label:
    signals
    .baz();
  }

After:
  void f() {
  label:
    signals.baz();
  }

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@276854 91177308-0d34-0410-b5e6-96231b3b80d8