Don't selectively undraw tiles in towers if backgrounds are off

The game for some reason had this thing where it would not draw the
diagonal background tiles if you had animated backgrounds turned off.
Which is weird, because spikes with that background are still drawn as
spikes with that background. And also, it doesn't do this for any of the
tower hallway rooms, which is inconsistent.

Better to simplify the logic in Render.cpp anyways by removing
graphics.drawtower_nobackground() and making it really clear what
exactly we'll do if backgrounds are turned off. ("Aren't we already not
drawing the background? What's this _nobackground() function for?")

desktop_version/src/Graphics.cpp

@@ -2441,20 +2441,6 @@ void Graphics::drawtowermap()
     }
 }
 
-void Graphics::drawtowermap_nobackground()
-{
-    int temp;
-    int yoff = lerp(map.oldypos, map.ypos);
-    for (int j = 0; j < 31; j++)
-    {
-        for (int i = 0; i < 40; i++)
-        {
-            temp = map.tower.at(i, j, yoff);
-            if (temp > 0 && temp<28) drawtile3(i * 8, (j * 8) - (yoff % 8), temp, map.colstate);
-        }
-    }
-}
-
 void Graphics::drawtowerspikes()
 {
     int spikeleveltop = lerp(map.oldspikeleveltop, map.spikeleveltop);

desktop_version/src/Graphics.h

@@ -191,8 +191,6 @@ public:
 
 	void drawtowermap();
 
-	void drawtowermap_nobackground();
-
 	void drawtowerspikes();
 
 	bool onscreen(int t);

desktop_version/src/Render.cpp

@@ -1382,13 +1382,12 @@ void gamerender()
             if (!game.colourblindmode)
             {
                 graphics.drawtowerbackground();
-                graphics.drawtowermap();
             }
             else
             {
                 FillRect(graphics.backBuffer,0x00000);
-                graphics.drawtowermap_nobackground();
             }
+            graphics.drawtowermap();
         }
         else
         {