Mel Gibson has become the highest paid star in Hollywood history. His latest salary: $25 million, according to the Sunday Times of London. The paper reports that Gibson received the bonanza for the Revolutionary War drama “The Patriot,” to be released this summer. The previous high star fee was Arnold Schwarzenegger’s $22-million salary for “End of Days.” Members of the $20 million club are reputed to be Leonardo DiCaprio (“The Beach”), Tom Hanks (“The Green Mile”), Jim Carrey (“The Truman Show”), Jack Nicholson (“As Good As It Gets”) and the omnipresent — in today’s Daily, at least — Julia Roberts (“Runaway Bride”). Actually, these are their upfront fees. Many more millions can be made from box-office percentages after the release of their pictures.