Previously the plugin system was obviously built around function
pointers, since a loaded plugin DLL would expose them statically.
This meant that the plugin classes I implemented also had to use
static methods, and all the variables had to be static as well.
This has been getting more and more annoying. So this commit is
an in-progress refactoring of AGS to allow for plugins to be
properly instance-based, and pointers to script methods will be
both a pointer to the plugin as well as the method name.
Thierry Crozat
Eugene Sandulenko
Paul Gilbert
Cameron Cawley