clang-format: Improve function parameter packing.

Before:
  void SomeLoooooooooooongFunction(
      std::unique_ptr<aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa>
          aaaaaaaaaaaaaaaaaaaaaaaaaa, int bbbbbbbbbbbbb);

After:
  void SomeLoooooooooooongFunction(
      std::unique_ptr<aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa>
          aaaaaaaaaaaaaaaaaaaaaaaaaa,
      int bbbbbbbbbbbbb);

llvm-svn: 221989