clang-format: Improve binary operator detection in macros.

Before:
  #define M(NAME) assert(!Context.Verifying &&#NAME);

After:
  #define M(NAME) assert(!Context.Verifying && #NAME);

This fixes llvm.org/PR16156.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194216 91177308-0d34-0410-b5e6-96231b3b80d8