More refactoring work: move the opening of a connection to the backend/
destination server into the conn.c module, so that it can be used by
both the forward.c and reverse.c modules.  Also delegate the work of handling
a USER command to the respective forward/reverse.c module, as they will
do different things.
More notes for the lab notework.
Just saw the first successful login via forward proxy configuration.  Woot!