Like bug reports contributed patches are forwarded to the developer mailing list. This is the link for submitting patches: http://sourceforge.net/tracker/?group_id=599&atid=300599.
You need to specify some parameters to the diff command for the patches to be useful. If you modified more than one file a patch created f.e. with ''diff -Naur unmodified_directory modified_directory >my_changes.patch'' will be fine, otherwise ''diff -u sourcefile.c.orig sourcefile.c >my_changes.patch'' will do.