Tor Messenger for Windows / OS X profile folder

Tor Messenger for Windows sets the profile folder for Instantbird to the default location in the %APPDATA%\Roaming\Instantbird directory. We should change the location of this folder to the Tor Messenger directory, like we do for Linux. (On Linux, the start-tor-messenger script takes care of this.)

Same for OS X, in ~/Library/Application\ Support/Instantbird