Revert "remove auto linking events which use gcc PMF extension"

This reverts commit aeca5c2ebab9ebe4857ca3db6469a1c410e45f58.
use another way to retrieve a PMF hash
add early-exit in CUnit::AddExperience
save username & passwd in NetProtocol, so it can reconnect w/o passing those again
fix 100% cpu usage in netcode thread
set game speed only when playerid is valid
fix sync-check in demos
some code improvements in netcode
UDPListener: allow to connect by hostname instead of just ips
add new `spring spring://username:passwd@hostname:port` syntax
* also changed --server argument to take a param (the ip/hostname listen to)
* removed -c/--client argument (was only needed in times when clients didn't retrieved their script.txt from the server)
* fixed direct connect window in SelectMenu
* by default listen to localhost:8452 now, so you can always connect to localhost started matches
* OS integration will follow (so you can start spring from browser!)
use exception in myGL.cpp