Update ant build to support JitPack
Update ant build to support JitPack

As suggested in #1, supporting deployment to JitPack does not involve migrating your to maven (JitPack supports ant), but would still allow others to include your library within their maven/gradle builds.

JitPack performs automated builds for every new tag in your repository, using whatever your build script is (maven, ant, you name it), and expects in return that this script produces a jar file. Currently, your ant script only produces a jar file if you explicitly indicate the "makedistrib" target (see eg. https://jitpack.io/com/github/pgdurand/jGAF/v2.4.0/build.log)

This change makes "makedistrib" the default ant target, and hopefully this should suffice for JitPack to retrieve the produced jar file.
NB: the jitpack doc does not say much about ant support, therefore I don't know where the .jar file must be located to be picked up, only one way to find out ;)
pgdurand/jGAF,pgdurand/jGAF,pgdurand/jGAF