Comment 51 for bug 1424769

I'm not sure, how to find out, but this is what I see in /var/log/Xorg.0.log
X.Org X Server 1.17.1
Release Date: 2015-02-10
[ 8.138] Build Operating System: Linux 3.19.0-28-generic x86_64 Ubuntu
...
[ 8.138] Current Operating System: Linux System360 3.19.0-39-generic #44~14.04.1-Ubuntu SMP Wed Dec 2 10:00:35 UTC 2015 x86_64
...
[ 8.138] xorg-server 2:1.17.1-0ubuntu3.1~trusty1 (For technical support please see http://www.ubuntu.com/support)

for mesa:
janko@System360:/var/log$ dpkg -l | grep mesa
ii libegl1-mesa-lts-vivid:amd64 10.5.9-2ubuntu1~trusty2 amd64 free implementation of the EGL API -- runtime
ii libgl1-mesa-dri-lts-vivid:amd64 10.5.9-2ubuntu1~trusty2 amd64 free implementation of the OpenGL API -- DRI modules
ii libgl1-mesa-glx-lts-vivid:amd64 10.5.9-2ubuntu1~trusty2 amd64 free implementation of the OpenGL API -- GLX runtime
ii libglapi-mesa-lts-vivid:amd64 10.5.9-2ubuntu1~trusty2 amd64 free implementation of the GL API -- shared library
ii libgles1-mesa-lts-vivid:amd64 10.5.9-2ubuntu1~trusty2 amd64 free implementation of the OpenGL|ES 1.x API -- runtime
ii libgles2-mesa-lts-vivid:amd64 10.5.9-2ubuntu1~trusty2 amd64 free implementation of the OpenGL|ES 2.x API -- runtime
ii libglu1-mesa:amd64 9.0.0-2 amd64 Mesa OpenGL utility library (GLU)
ii libwayland-egl1-mesa-lts-vivid:amd64 10.5.9-2ubuntu1~trusty2 amd64 implementation of the Wayland EGL platform -- runtime

BTW, I tried to revert to cleaninstalled OS and install virtualbox-guest-dkms - it installed correctly, but virtualbox-guest-x11 cannot be installed due to a broken dependency with xorg-video-abi-15.
I tried to install xserver-xorg-core, but there are yet another unmet dependencies, which I'm not able to resolve.