What you need to update to move from 2.5 to 2.9? I have all the files, and updated the STR_SOLDIER entry as well.
Not sure whom was this question addressed, so I'll answer all three I can think of:
1. What do I (=Meridian) need to do to upgrade: I need to be able to compile this whole thing correctly (in vs2015 with c++11). In my endless stupidity, I am still not able to do it. However, Yankes has prepared a recent build (2016-02-13), which you can download also from my thread (
https://drive.google.com/open?id=0B8itkFQbhj-YSXZ3YnhsRWdwMzg). I believe he'll gladly help us build it until I figure out how to do it myself.
2. What do you (=Dioxine) need to do to upgrade. Go through list of changes in vanilla I provided somewhere earlier and make sure you're compatible. If you're compatible with that, you should be OK. Yankes didn't introduce any breaking changes between 2.5 and 2.9... and I didn't introduce any changes at all between 2.5 and 2.9.
3. What do they (=Aldi or anyone else compiling on their own) need to do to upgrade... they need to wait for you releasing new version of X-PirateZ and then compile my 2.9 OXCE+ branch (
https://github.com/MeridianOXC/OpenXcom/tree/oxce2.9-plus-proto) and use that (instead of 2.5 branch).