Moved all the datablock-twiddling version patching magic to the "after_liblink" version patching function. Apparently the problem was that many of the old pointers had not been fixed up at that point, causing problems if relying on accessing their contents.
Fix: Temporary fix for crashes when moving GP keyframes when toggling Onion Skinning
ANIM_list_elem_update() was not doing anything as ale->id was null, and we were filtering the channels by "animdata" blocks (i.e. the GP datablocks). While technically what we're doing here isn't totally correct (I'll need to come up with a better fix tomorrow), this will be a good quick-fix for the crashes they animators are currently getting.
In some tablets when the user ends the stroke the tablet send several events with a pressure of 0 or with very low values. These low pressure values produce weird lines at the end of the stroke.