Codechange: Place gamelog into its own class, along with internal data.

Data is now stored in vectors to avoid manual memory management and
passing lengths around.

Change: rework GLOG chunk to be more like the rest

Basically it is very similar to Vehicles, where there first is
a type field, followed by data of that type. So this commit makes
it looks like how Vehicles solved that.
This removes a lot of custom "keeping track of length" stuff.