Use XGetWindowAttributes for window size

Use XGetWindowAttributes in place of glXQueryDrawable.
Mesa glXQueryDrawable has trouble reading width and height.
Avoid glX in vogl_get_default_framebuffer_attribs

Use OpenGL calls instead of glX calls for vogl_get_default_framebuffer_attribs.
That will be portable to systems not using glX.
Exclude imaging subset and pixel transfer
PARTIAL: Start trying to integrate "pxfmt" into VOGL.