[calendar] [mozilla 1.x] if native calendar app is available, and mozilla calendar there,
show chrome to launch a native calendar, if specified by a pref.
this "tasks" extension can be extended for other tasks.
NOT PART OF THE BUILD
r/sr/a=sspitzer
git-svn-id: svn://10.0.0.236/trunk@150126 18797224-902f-48f8-a5cc-f745e15eee43
