Update UPGRADE.txt file

git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/13@420607 f38db490-d61c-443f-a65b-d21fe96a405b
Update CHANGES file

git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/13@420609 f38db490-d61c-443f-a65b-d21fe96a405b