Fixed video flickering in the campaign intro screen.

git-svn-id: http://svn.code.sf.net/p/vcmi/code/trunk/@3793 4dfc6b2a-8b31-0410-aa91-d6c70e3ac834
Release date in the changelog.

git-svn-id: http://svn.code.sf.net/p/vcmi/code/trunk/@3794 4dfc6b2a-8b31-0410-aa91-d6c70e3ac834