Adding news of 2.1.12 release

git-svn-id: https://svn.apache.org/repos/asf/cocoon/trunk@1458963 13f79535-47bb-0310-9956-ffa450edef68
Missing info on home page about latest C2.1 release

git-svn-id: https://svn.apache.org/repos/asf/cocoon/trunk@1458967 13f79535-47bb-0310-9956-ffa450edef68