ant changes between 1.5 and 1.6

I've only used the 1.6.1 version of ant, but one of my co-workers has questions about how ant changed between 1.5 and 1.6. He has not been able to find documentation on what changes were implemented. In particular he is wondering what changed with ant-junit.jar and name changes on xerces. Can anyone point me towards documentation that will help him understand these changes?
Thank you!

1.5.1: http://archive.apache.org/dist/ant/binaries/RELEASE-NOTES-1.5.1.html
1.6.1: http://ftp.plig.net/pub/apache/dist/ant/README.html
As far as I remember the junit task was an optional task before 1.5.4, and a core task from then on. Don't know about xerces - but it should be mentioned in the docs somewhere.