[gl2ps] [patch] Enable use without an OpenGL context

[Andreas Weber]

Hi David,

Am 12.01.2016 um 22:08 schrieb David Lonie:
> I maintain the GL2PS export implementation in VTK, and we recently
> revamped our rendering engine to use newer OpenGL APIs, and the
> versions we're targeting have deprecated the OpenGL feedback buffer.

I'm very unexperienced with OpenGL internals so this might be a silly
question. If I read the topic, does this mean that it is now possible to
use gl2ps without OpenGL context, for example on a headless server
without X running? In my words something like "offscreen rendering"?

Thank you, Andy