clang-format: Remove empty lines at the beginning of blocks.

They very rarely aid readability.

Formatting:
  void f() {

    if (a) {

      f();

    }

  }

Now leads to:
  void f() {
    if (a) {
      f();
    }
  }

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@204460 91177308-0d34-0410-b5e6-96231b3b80d8