Add some @since tags to an interface we've told people they could
implement for custom plugins - bad example of backwards
incompatibility at work (there's been no release since 1.2 that didn't
change the interface and there is no single method of the 1.2 release
left in that interface).
git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@272402 13f79535-47bb-0310-9956-ffa450edef68