VERSION: Use the "SIM_BUILD_NIGHTLY" designation for all commits henceforth except for release candidate or release builds
CHANGE: Default file format is now zipped rather than bzip2, which is faster to save and only moderately larger
CHANGE: Greatly reduce the proportion of mail generated to passengers (approx. 1:200)
CHANGE: Only passengers will be discarded when their waiting time exceeds thrice their journey time: mail and goods will only be discarded when the waiting time exceeds the base maximum.