Graphics drivers

Use set_gfx_mode to select an OpenGL mode as normal, but using e.g. More...GFX_OPENGL as the driver. The virtual width and height are ignored. To set the colour depth, use allegro_gl_set (AGL_COLOR_DEPTH, xxx). However if the color depth is not set by allegro_gl_set(), AllegroGL will refer to the value set by the last call to set_color_depth().

Allegro modes are still available. Use of GFX_AUTODETECT or GFX_AUTODETECT_WINDOWED will select Allegro modes, and not OpenGL modes.

---