Filip Roséen authored Dec 19, 2016 and Thomas Guillem committed Dec 19, 2016

Given that there are places in the codebase that just require a
created object of type vlc_gl_t ("gl"), these changes split the object
creation into two functions:

 - vlc_gl_Create: a simple wrapper around vlc_custom_create
 - vlc_gl_ModuleCreate: creates a vlc_gl_t with an associated
                        module/surface.

refs #17795

Signed-off-by: Thomas Guillem <thomas@gllm.fr>