/*
* Get the current X11 Visual.
*
* Note: This method is not available unless Imlib2-Ruby was compiled
* with X11 support. You can check the constant Imlib2::X11_SUPPORT to
* see if X11 support is available.
*
* Examples:
* visual = context.get_visual
* visual = context.visual
*
*/
static VALUE ctx_visual(VALUE self) {