Get less confused by trailing comma in Google style.

The formatter can now format:
void aaaaaaaaaaaaaaaaaa(int level,
                        double *min_x,
                        double *max_x,
                        double *min_y,
                        double *max_y,
                        double *min_z,
                        double *max_z, ) {
}

Although this is invalid code, it frequently happens during development and
clang-format should be nicer :-).

llvm-svn: 175151