NEWSFLASH: It's hot out. O.K., that obligatory small talk out of the way, check out one of the 5.5 bathrooms at this just-listed Brookline manse in Fisher Hill. It has not only a deep-soaking tub and natural sunlight downright flooding on in; it's also got a fireplace. We don't know how we feel about that: hot and cold adjectival phrases spring to mind, but we're too overheated to really think. Otherwise, the 5,836-square-foot house has six bedrooms, a game room, a chef's kitchen, a library (with another fireplace!), an au pair suite in the basement, and a two-car garage. It last traded way back in December 1993 for the low, low price of $470,000. Now asking $2,999,000.