Drop createContext and destroyContext from DRIinterfaceMethods.

As for createDrawable and destroyDrawable, these functions immediately
upon entry to driCreateNewContext and immediately before exit from
driDestroyContext.  Instead of passing function pointers back and forth
just obtain the drm_context_t prior to calling DRIscreen::createNewContext
and pass it as a parameter.

This change also lets us keep the DRI context XID in the libGL loader only.

include/GL/internal/dri_interface.h

@@ -183,17 +183,6 @@ struct __DRIinterfaceMethodsRec {
      */
     /*@{*/
 
-    /**
-     * Create the server-side portion of the GL context.
-     */
-    GLboolean (* createContext)( __DRIscreen *screen,
-        int configID, void * contextID, drm_context_t * hw_context );
-
-    /**
-     * Destroy the server-side portion of the GL context.
-     */
-    GLboolean (* destroyContext)( __DRIscreen *screen, __DRIid context );
-
     /**
      * This function is used to get information about the position, size, and
      * clip rects of a drawable.
@@ -345,7 +334,8 @@ struct __DRIscreenRec {
     void * (*createNewContext)(__DRIscreen *screen,
 			       const __GLcontextModes *modes,
 			       int render_type,
-			       void *sharedPrivate, __DRIcontext *pctx);
+			       void *sharedPrivate,
+			       drm_context_t hwContext, __DRIcontext *pctx);
 
     /**
      * Method to override base texture image with a driver specific 'offset'.