Android L requires executables to be compiled with PIE support, so we'll
have to ship two Tor binaries.

Of course, not all devices support Bluetooth...

See
https://developer.android.com/guide/topics/ui/notifiers/notifications.html#NotificationResponse

This makes the contact list behave how alpha testers expected: touching
a contact shows private messages exchanged with the contact.

Some Android devices require a lock to be held while using multicast, to
disable the packet filter that normally filters out multicast packets.

Fields in Android UI objects that are accessed from background threads
must be declared volatile. UI objects use data attached to DB events to
avoid DB lookups, which complicates the UI code but should improve
performance.