The NYPD hate-crimes unit is investigating threats made to a Brooklyn Civil Court judge who was sworn in on a Koran, The Post has learned. Judge Carolyn Walker-Diallo got two calls at 11:30 a.m. Tuesday at the courthouse on Schermerhorn Street, law enforcement sources said on Wednesday ... David Bookstaver, a spokesman for the state's courts, said judges need only swear an oath of office that they will uphold the law, and that there are no requirements to use a religious text. "You can be sworn in on a comic book. You don't need to sign in on anything; you...