gemrb: bump and maintentance

Should compile on all platforms, but there's no need to burden hydra with something so obscure.

Upstream tuning in from the Lj hackfest
Seemed pointless for such a quick and obscure build. Plus, I'm going away for a month in a week, so I don't have time to investigate and fix any build bot fallout. I can do that before the next release, but here it was not even a change — with no platforms specified before, hydra was disabled anyway.