systems/x11: fix incorrect API usage (dfb_surface_get_data_offsets)

.../systems/x11/primary.c: In function 'update_screen':
.../systems/x11/primary.c:878:41: warning: passing argument 1 of 'dfb_surface_get_data_offsets' from incompatible pointer type [enabled by default]
.../src/core/surface.h:491:1: note: expected 'const struct CoreSurfaceConfig * const' but argument is of type 'struct CoreSurface *'

This also fixes a few crashes when running the cairo test suite against
the DirectFB backend.

Author: andred

systems/x11/primary.c

@@ -874,7 +874,7 @@ update_screen( DFBX11 *x11, const DFBRectangle *clip, CoreSurfaceBufferLock *loc
 
           dst = xw->virtualscreen + rect.x * xw->bpp + (rect.y + offset) * ximage->bytes_per_line;
 
-          dfb_surface_get_data_offsets( allocation->surface, lock->addr, lock->pitch, rect.x, rect.y,
+          dfb_surface_get_data_offsets( &allocation->config, lock->addr, lock->pitch, rect.x, rect.y,
                                         3, srces, pitches );
 
           switch (xw->depth) {