Implement GLX and X functionality through Mesa's EGL interface. This
requires multiple OpenGL contexts and in turn GEM context support in
libdrm/iris, as implemented in libdrm and intel_gpu_drv.
Update recipes and machine.vbox6 files accordingly,
issue #4380
There are some subtle incompatibilities in VirtualBox 6 with settings we
used in version 5. Therefore, the vbox6 package uses machine.vbox6 as
configuration file. An example configuration is provided by the
raw/vbox6 package.
Issue #4281
