Reset available offscreen segment save function pointer. (Not a functional

change, just cleaning up a bit)
Reset the screen->memory_base value when frame buffer is remapped. This
    makes sure new off-screen allocations point at the newly mapped region
    rather than the old (now unmapped) region.

hw/kdrive/src/koffscreen.c

@@ -259,6 +259,7 @@ KdOffscreenFree (ScreenPtr pScreen, KdOffscreenArea *area)
     KdOffscreenValidate (pScreen);
 
     area->state = KdOffscreenAvail;
+    area->save = 0;
 
     /*
      * Find previous area

hw/kdrive/vesa/vesa.c

@@ -1360,6 +1360,7 @@ vesaEnable(ScreenPtr pScreen)
 	    if (!pscr->fb)
 		return FALSE;
 	    screen->fb[0].frameBuffer = (CARD8 *)(pscr->fb);
+	    screen->memory_base = pscr->fb;
 	    /*
 	     * Set frame buffer mapping
 	     */