This is because several libraries have separate binaries, and so are
linked with different command-line arguments, just like gint is linked
with -lgint-fx on one side and -lgint-cg on the other.
This makes it possible to change PREFIX at the last minute when running
install, effectively installing the files into a false packaging root
while retaining the same contents as if installed normally.
This change enhances the style of fxconv by using more classes and
generally more Pythonic constructions.
It also introduces image conversion for fx-CG 50, requiring the use
of --fx or --cg to specify the target machine with -i. The default
is set to --fx to maintain compatibility with older Makefiles.