Actually report server version mismatches

Incompatible servers get dropped from the server list. It
turns out the server list is also used when connecting
directly to a server. This meant that if you tried
connecting to a server that was incompatible, you'd just
get an infinite connection screen, as if the server was
completely unreachable.

Now it won't drop the server if you are directly
connecting to it. I also copied some incompatibility
messages from HandleConnect.