clang-format: Remove empty lines after visibility modifiers.

Formatting:
  class C {
  public:

    f();
  };

Now leads to:
  class C {
  public:
    f();
  };

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192062 91177308-0d34-0410-b5e6-96231b3b80d8