Squashes two related patches from master:

Don't use rtl::Reference for the global / list state, so the
ref-count reflects the number of real users.
Hold a reference during ~OpenGLContext.

Fix mis-use in:
gltf rendering, OpenGL canvas, GL transitions & GL capable (charts)
Avoid GLX operations on un-initialized contexts.
Signed-off-by: Miklos Vajna <vmiklos@collabora.co.uk>

Conflicts:
	vcl/source/opengl/OpenGLContext.cxx
	vcl/workben/vcldemo.cxx
	canvas/source/opengl/ogl_spritedevicehelper.hxx

Change-Id: I7ea29b544d53bb80b25fa6663d39f345bf8f4e64