Mismatched headers

Some libraries, like GTK+, assume the use of headers for the version targetted. In other words, even if the "Since 2.4" functions are avoided, if it is compiled against the GTK+ 2.4 headers there is a risk of gaining an implicit dependency on GTK+ 2.4.

The only current solution to this is to get a copy of the older headers for the version targetted and drop them into the apbuild directory so they are searched before your system headers are.