for vulkan widget, set handle->lowlevel->copy_buffer to 0 at nishi's suggestion (it still flickers when I resize)

git-svn-id: http://svn2.nishi.boats/svn/milsko/trunk@116 b9cfdab3-6d41-4d17-bbe4-086880011989

src/widget/vulkan.c

@@ -99,6 +99,8 @@ static void create(MwWidget handle) {
 		return;
 	}
 
+	handle->lowlevel->copy_buffer = 0;
+
 	handle->internal = o;
 	MwSetDefault(handle);
 }