Angus made al_Asset work with AssImp version 3, but wasn't able to make the preprocessor auto-detect whether AssImp 2 or 3 is installed. We should either
Stop supporting AssImp 2 and assume AssImp 3 exclusively, or
FIgure out a way for the build system to detect which AssImp is installed (e.g., checking the existence of a file that appears in only one of the two)
Angus made al_Asset work with AssImp version 3, but wasn't able to make the preprocessor auto-detect whether AssImp 2 or 3 is installed. We should either