Teach clang-format to understand static_asserts better.

Teach clang-format to understand static_asserts better.

Before:
  template <bool B, bool C>
  class A {
    static_assert(B &&C, "Something is wrong");
  };

After:
  template <bool B, bool C>
  class A {
    static_assert(B && C, "Something is wrong");
  };

(Note the spacing around '&&'). Also change the identifier table to always
understand all C++11 keywords (which seems like the right thing to do).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@187589 91177308-0d34-0410-b5e6-96231b3b80d8