Use a different magic for memory DCs and get rid of the DC_MEMORY
flag.

diff --git a/graphics/x11drv/init.c b/graphics/x11drv/init.c
index 7577582..944ec4c 100644
--- a/graphics/x11drv/init.c
+++ b/graphics/x11drv/init.c
@@ -103,7 +103,7 @@
     physDev->hdc = dc->hSelf;
     physDev->dc  = dc;  /* FIXME */
 
-    if (dc->flags & DC_MEMORY)
+    if (GetObjectType( dc->hSelf ) == OBJ_MEMDC)
     {
         physDev->drawable  = BITMAP_stock_pixmap;
     }