[MlMt] composer window placement

[John D. Muccigrosso]

New-message windows in MM2 seem to get placed a little right and lower 
than the previous one, until one gets as far right and down as possible 
and then they stay there. Makes me think they’re going off-screen. 
I’d prefer MM2 to remember where I placed one the last time and always 
use that. Or at least restart the placement (as I think Mail.app does).

Thanks.

John