Today you need to exit fullscreen and then click on minimize button,
im unsure this option has been available before in the context menu,
but it sounded like that from the reporter of the issue.
Previous Windows viewer used the normal system menu with some additions, so they had several things like move, minimize and close.
Fixed in r30634.
Verified using build 4854 on both Linux and Windows platform. Minimize works as expected.
Now also tested on Mac OS X platform. Works as expected.