fix IVY-1457 XmlModuleDescriptorWritter doesn't support fully extra infos elements

ModuleDescriptor.getExtraInfo() is now deprecated as name of the tag was used as key. Tag name can't be used as key as extra info elements can be non unique.

git-svn-id: https://svn.apache.org/repos/asf/ant/ivy/core/trunk@1557557 13f79535-47bb-0310-9956-ffa450edef68
add IVY-1457 on CHANGES.txt

git-svn-id: https://svn.apache.org/repos/asf/ant/ivy/core/trunk@1557559 13f79535-47bb-0310-9956-ffa450edef68