Make clang-format slightly more willing to break before trailing annotations.

Specifically, prefer breaking before trailing annotations over breaking
before the first parameter.

Before:
  void ffffffffffffffffffffffff(
      int aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
      int aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa) OVERRIDE;

After:
  void ffffffffffffffffffffffff(int aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
                                int aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa)
      OVERRIDE;

llvm-svn: 192983