Hanohano Room   As we went to press, the Hanohano Room, on the 30th floor of the Sheraton Waikiki hotel, was undergoing renovation, a change of concept and menu. What we can guarantee is that it will continue to see many a marriage proposal and anniversary celebration, since this multiwindowed room is among the city's most romantic, looking out in both directions, toward Diamond Head and down the length of Waikiki Beach, offering breathtaking sunsets. There's music nightly.  Sheraton Waikiki, 2255 Kalakaua Ave. 922-4422. 5:30-9 p.m. daily. Bar: 5-11 p.m. Reservations recommended. Valet and self-parking. AX, DC, DS, JCB, MC, VS. No checks. $$$$.  Web site: www.sheratonwaikiki.com