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

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);

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@291434 91177308-0d34-0410-b5e6-96231b3b80d8