Update 5.2.6

I've uploaded a minor patch, hoping to avoid some of the saved campaign corruptions that a small number of players have experienced. Basically the game used to save itself to disk after every phase during the scenario, which isn't at all required, so now it drastically reduces the number of times that it is writing to disc, hopefully avoiding these corrupted saved campaign files. I had already implemented this for 6.0, but it was an easy fix to add to the current 5.x branch.