add servertime to the gametype api

Version 0.62 of racesow.

* port racesow to stay compatible with the last warsow version (0.62)
* fix a few bugs that were causing server crashes or freezes
* optimize database queries to reduce "end of race" computations
* improvements to the racesow hud thanks to Joki (most of them have also been
  included in warsow)