Add option to bind gui rpc to a specific network interface rather than binding INADDR_ANY

[Martijn]

Boinc currently lacks the possibility to explicitly specify on which network interface its rpc gui interface must be bound.

An option similar to '--gui_rpc_port' should be introduced, something like '--gui_rpc_address'.

[Nicolas]

In my opinion: if you're experienced enough to need binding to a different network interface, and to know it's currently using INADDR_ANY (and to know what INADDR_ANY even is), you're probably experienced enough to do the code change yourself too :)

[davea]

Please send me a patch for this