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

See bug #27.

The TransportReader/Writer's dispose() method should handle that, and
ConnectionManager is responsible for calling it.

This makes it more likely that connections will be closed cleanly.
However, the interrupt() method is currently ineffective for incoming
sessions as it won't interrupt a blocking read, e.g. when the packet
reader is waiting for a packet.

Because that's what it does.

This can be used to combine e.g. the platform's SecureRandom
implementation with our own, so that a weakness in either source doesn't
harm security as long as the other source is strong.

This should make it easier for people to build the project with a freshly
downloaded ADT Bundle.

Two changes have been made to Tor:

1. Set can_complete_circuit to false when the network is disabled, and
don't try to build introduction circuits while can_complete_circuit is
false. This avoids a situation where Tor tries to build introduction
circuits as soon as the network is re-enabled, all the circuits fail,
and then Tor waits 5 minutes before trying to build more.

2. Added a FORGETHS command to the control protocol which clears any
cached client state relating to a specified hidden service. This can be
used to flush state that's likely to be stale before trying to connect
to a hidden service with an unstable network connection.

Support for the FORGETHS command was also added to jtorctl.