update windows build to use jre7_u21, partly fixes widely reported focus problems on win7 and 8
The focus manager is causing all sorts of problems on some win7/8 installs we've heard it alot in the forums, but I was able to work with a user to narrow down that it's the focus manager causing the issues.
I'm not sure yet of all the reprecussions of disabling this but I'm going to make a build without for windows and test.