Remove GetMSC DriverAPI function.

The DriverAPI is internal to the DRI drivers and GetDrawableMSC
obsoletes GetMSC.  Also, since the DRI driver interface has not yet
been released, just drop the getMSC function from the DRI interface
instead using the ABI preserving version mechanism.

Finally, using void pointer privates in the DRI interface is not allowed,
always pass the actual types around (__DRIdrawable in this case) to
enhance type safety and readability of the code.

include/GL/internal/dri_interface.h

@@ -171,16 +171,10 @@ struct __DRIframeTrackingExtensionRec {
  * Used by drivers that implement the GLX_SGI_video_sync extension.
  */
 #define __DRI_MEDIA_STREAM_COUNTER "DRI_MediaStreamCounter"
-#define __DRI_MEDIA_STREAM_COUNTER_VERSION 2
+#define __DRI_MEDIA_STREAM_COUNTER_VERSION 1
 struct __DRImediaStreamCounterExtensionRec {
     __DRIextension base;
 
-    /**
-     * Get the number of vertical refreshes since some point in time before
-     * this function was first called (i.e., system start up).
-     */
-    int (*getMSC)(__DRIscreen *screen, int64_t *msc);
-
     /**
      * Wait for the MSC to equal target_msc, or, if that has already passed,
      * the next time (MSC % divisor) is equal to remainder.  If divisor is
@@ -192,15 +186,10 @@ struct __DRImediaStreamCounterExtensionRec {
 		      int64_t * msc, int64_t * sbc);
 
     /**
-     * Like the screen version of getMSC, but also takes a drawable so that
-     * the appropriate pipe's counter can be retrieved.
-     *
      * Get the number of vertical refreshes since some point in time before
      * this function was first called (i.e., system start up).
-     *
-     * \since Internal API version 2
      */
-    int (*getDrawableMSC)(__DRIscreen *screen, void *drawablePrivate,
+    int (*getDrawableMSC)(__DRIscreen *screen, __DRIdrawable *drawable,
 			  int64_t *msc);
 };