clang-format: Improve pointer/reference detection.

Before (with left pointer alignment):
  void f(int i = 0, SomeType* *temps = NULL);

After:
  void f(int i = 0, SomeType** temps = NULL);

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@214071 91177308-0d34-0410-b5e6-96231b3b80d8