add test for VR HUD/sub-titles
fix issue in previous commit, partial string use %.8s not %8.s
use long long int in b3Clock
fix warning/error in pointer alignment in serialization
Fix pybullet Windows compilation.
(thanks to bkeys/https://github.com/bulletphysics/bullet3/pull/687)
Add option to have Z as up-axis for VR examples.
Add OpenVR LICENSE + README file
Don't crash VR app when no HMD is detected, just exit.
For now, don't request debug lines in client, it slows down physics server in VR mode too much.