Add -addr flag to compiled output

For the garbled circuit back ends it is now possible to specify the
network address to bind/connect to.  This will allow a server with
multiple network interfaces to choose the interface, and allow clients
and servers to operate on different machines.

Example server invocation:

    go run foo_*.go -id 1 -addr 127.0.0.1:3333 6

Example client invocation:

    go run foo_*.go -id 0 -addr 192.168.0.5:3333 10