clang-format: Improve support for override/final as variable names.

Before:
  bool a = f() &&override.f();
  bool a = f() &&final.f();
  void f(const MyOverride & override);
  void f(const MyFinal & final);

After:
  bool a = f() && override.f();
  bool a = f() && final.f();
  void f(const MyOverride &override);
  void f(const MyFinal &final);

llvm-svn: 291434