Update some ANT plugins:
- make SVN version configurable: As svnkit 1.8 does not support svn 1.7 WCs and vice versa, if you use an 1.8 WC, you have to manually pass -Dsvnkit.version=1.8.0 (unless I find a better solution...)
- Update Groovy
- Update Pegdown
- LUCENE-5243: Update Clover to released version 3.2.0 (no more snapshot)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1547661 13f79535-47bb-0310-9956-ffa450edef68