[REL] Update changelog.txt for 12.0alpha

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/12.x@47991 b456876b-0849-0410-b77d-98878d47e9d5
[REL] Update copyright.txt for 12.0alpha

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/12.x@47992 b456876b-0849-0410-b77d-98878d47e9d5