message: Added missing include to <cctype> for 'std::isalnum'
  Should fix the failing Windows bots.
diff: // C Includes
  // C++ Includes
  +#include <cctype> // for alnum
  // Other libraries and framework includes
  #include "clang/AST/ASTContext.h"
  #include "clang/AST/ASTDiagnostic.h"
  