is_mp_sync fix

Fixes multiplayer synchronisation issue caused by a bug introduced in is_mp_sync by the ENet code.
See also the forum thread http://www.7kfans.com/forums/viewtopic.php?p=4973#p4973 for more information.

The first 4 patches are for improved debugging (and these helped me get to the cause of it).
The last patch makes all clients adopt the host's frame speed.