v2.30 and changes for buster

[Paddy]

I've just released v2.30 on github and pypi.python.org There are a couple of enhancements such as X11 window title and billboard quads in MergeShape, but a significant change is that the RPi4 won't have access to the old broadcom driver so there is now additional code to check if the 'new' hardware accelerated GL driver is enabled, in which case pi3d should use X11 instead of bcm_host. Unfortuneatly I've added a dependency by using glxinfo to do the check, so on a clean buster sd card I had to

sudo apt-get install mesa-utils

I will try to update a version without this dependency as soon as poss.