Version 0.99.4 breaks backward compatibility. Especially, you should
note that it works only with GIMP 0.99.19 and later.
If you have any GTK programs compiled on your system, they will almost
definately not run after you install this version of GTK.
This version will be very similar to GTK 1.0, and as such, you can
expect only bug fixes in future 0.99 versions.