[maven-release-plugin] prepare release maven-war-plugin-2.6

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1636977 13f79535-47bb-0310-9956-ffa450edef68
[maven-release-plugin] rollback the release of maven-war-plugin-2.6

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1636978 13f79535-47bb-0310-9956-ffa450edef68
MPMD-191: Update to PMD 5.2.1

* Because PMD now comes with multiple moduls depending on the language
  we must not only update the version.
* The API for detecting languages was changed as well.
* Additionally, rules in PMD do not end on `Rule` anymore, so
  custom configurations need to be adapted as well.

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1636987 13f79535-47bb-0310-9956-ffa450edef68