Refactor tower background to use a separate object instead

Previously, the tower background was controlled by a disparate set of
attributes on Graphics and mapclass, and wasn't really encapsulated. (If
that's what that word means, I don't particularly care about
object-oriented lingo.) But now, all relevant things that a tower
background has has been put into a TowerBG struct, so it will be easy to
make multiple copies without having to duplicate the code that handles
it.

desktop_version/src/Map.h

@@ -9,6 +9,7 @@
 #include "Otherlevel.h"
 #include "Spacestation2.h"
 #include "Tower.h"
+#include "TowerBG.h"
 #include "WarpClass.h"
 
 struct Roomtext
@@ -47,7 +48,7 @@ public:
 
     void setcol(const int r1, const int g1, const int b1 , const int r2, const  int g2, const int b2, const int c);
 
-    void updatetowerglow();
+    void updatetowerglow(TowerBG& bg_obj);
 
     void nexttowercolour();
 
@@ -102,21 +103,17 @@ public:
     bool towermode;
     float ypos;
     float oldypos;
-    int bypos;
     int cameramode;
     int cameraseek, cameraseekframe;
     int resumedelay;
     bool minitowermode;
-    int scrolldir;
 
     //This is the old colour cycle
     int r, g,b;
-    int colstate, colstatedelay;
+    int colstatedelay;
     int colsuperstate;
     int spikeleveltop, spikelevelbottom;
     int oldspikeleveltop, oldspikelevelbottom;
-    bool tdrawback;
-    int bscroll;
     //final level navigation
     int finalx;
     int finaly;
@@ -172,18 +169,8 @@ public:
     int kludge_bypos;
     int kludge_colstate;
     int kludge_scrolldir;
-    void inline bg_to_kludge()
-    {
-        kludge_bypos = bypos;
-        kludge_colstate = colstate;
-        kludge_scrolldir = scrolldir;
-    }
-    void inline kludge_to_bg()
-    {
-        bypos = kludge_bypos;
-        colstate = kludge_colstate;
-        scrolldir = kludge_scrolldir;
-    }
+    void bg_to_kludge();
+    void kludge_to_bg();
 };
 
 #ifndef MAP_DEFINITION