quick patch to properly detect major swf versions based on the decimal v...

...alue of the fourth swf byte

Could perhaps be a simpler fix for https://github.com/revive-adserver/revive-adserver/issues/104

Code taken from Steven Henk Don's blog post here: http://www.shdon.com/blog/2012/12/03/bugfix-for-handling-of-flash-content-in-openx (as the post suggests, it might need further tweaking for Flash Player 12)