clang-format: Improve operator and template recognition.

Before:
  static_assert(is_convertible < A &&, B > ::value, "AAA");

After:
  static_assert(is_convertible<A &&, B>::value, "AAA");

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@214075 91177308-0d34-0410-b5e6-96231b3b80d8