Create driver-independent CRTC-based cursor layer.

This moves most of the cursor management code out of the intel driver and
into the general server code. Of course, the hope is that this code will be
useful for other driver writers as well.

Check out xf86Crtc.h for the usage information, making sure you add the
needed hooks to the crtc funcs structure for your driver.
(cherry picked from commit 4d81c99a4660a0bf9014f789de55edabd185bd14)

hw/xfree86/loader/xf86sym.c

@@ -1220,6 +1220,11 @@ _X_HIDDEN void *xfree86LookupTab[] = {
     SYMFUNC(xf86RandR12SetConfig)
     SYMFUNC(xf86RandR12SetRotations)
 #endif
+    SYMFUNC(xf86_cursors_init)
+    SYMFUNC(xf86_reload_cursors)
+    SYMFUNC(xf86_show_cursors)
+    SYMFUNC(xf86_hide_cursors)
+    SYMFUNC(xf86_cursors_fini)
 
     SYMFUNC(xf86DoEDID_DDC1)
     SYMFUNC(xf86DoEDID_DDC2)