Update R4.0.0 — Source of the Nile Digital Edition Steam update #1096368

* R4.0.0 is a substantial code rebuild. Unfortunately, due to software idiosyncrasies, it is not backward compatible with R3 saves. - I have tested this build for bugs as much as possible. Hopefully, none have slipped through the net. * Fixed a bug that would cause the game lock up if in mounted travel-mode, both camels and horses were present, and a man was killed or discharged. * Introduced an "animal loss hierarchy" to the mounted expeditions code, based on animal health and terrain bias, rather than using the old "random" method. * Previously, the explorer would automatically become a bearer if the last bearer died, in order to avoid too many losses of pack-animals. - The player is now given a choice if askaris are present, in case losing 1 askari per turn seems too high a price for a pack animal. - The event is now triggered by a "bearer to animal" ratio, rather than being down to t...