If HBO kahuna Colin Callender seems a tad taciturn, it may be because he’s missing his favorite toy. For months, Time Warner vituperative shareholder Carl Icahn kvetched about the NYC palace posing as its headquarters, the corporate support departments more crowded than Barney’s Santa Monica hangar sales, and other wasteful spending. Now Callender is telling friends that HBO has lost its pet G5. Yes, Icahn also targeted those multiples of corporate jets. But, sheesh, what’s one Gulfstream more or less?