(svn r10373) [0.5] -Backport from trunk (r10306, r10311, r10317, r10339, r10344):
- Fix: Acceleration for trains on slopes is not calculated properly [FS#786] (r10317, r10344)
- Fix: Rail could be destroyed when building tunnels (r10306)

# set the server port to the default value
server_port = 3979