added x11-drivers/xf86-video-virtualbox-4.3.4 from official tree (based 4.3.2).
xf86-video-virtualbox-4.3.4: added FreeBSD support (includes fix for 10.0).
overlay.xml -- changed http --> git
added app-emulation/virtualbox-guest-additions-4.3.4 from official tree (based 4.3.2).
virtualbox-guest-additions-4.3.4: added FreeBSD support (includes fix for 10.0).