Paint DFHack in corner if supported.

library/Core.cpp

@@ -772,9 +772,29 @@ void Core::Resume()
     AccessMutex->unlock();
 }
 
+struct screen_tile
+{
+    unsigned char symbol;
+    unsigned char front;
+    unsigned char back;
+    unsigned char bright;
+};
+
+void screen_paint (int x, int y, uint8_t symbol)
+{
+    int tile = x * df::global::gps->dimy + y;
+    screen_tile *s = (screen_tile *) (df::global::gps->screen + tile*4);
+    s->symbol = symbol;
+}
+
 int Core::TileUpdate()
 {
-    //df::global::gps->;
+    screen_paint(0,0,'D');
+    screen_paint(1,0,'F');
+    screen_paint(2,0,'H');
+    screen_paint(3,0,'a');
+    screen_paint(4,0,'c');
+    screen_paint(5,0,'k');
     return true;
 }