Explicitly declare void for all void parameter functions (#628)

Apparently in C, if you have `void test();`, it's completely okay to do
`test(2);`. The function will take in the argument, but just discard it
and throw it away. It's like a trash can, and a rude one at that. If you
declare it like `void test(void);`, this is prevented.

This is not a problem in C++ - doing `void test();` and `test(2);` is
guaranteed to result in a compile error (this also means that right now,
at least in all `.cpp` files, nobody is ever calling a void parameter
function with arguments and having their arguments be thrown away).
However, we may not be using C++ in the future, so I just want to lay
down the precedent that if a function takes in no arguments, you must
explicitly declare it as such.

I would've added `-Wstrict-prototypes`, but it produces an annoying
warning message saying it doesn't work in C++ mode if you're compiling
in C++ mode. So it can be added later.

desktop_version/src/Map.h

@@ -21,7 +21,7 @@ struct Roomtext
 class mapclass
 {
 public:
-    mapclass();
+    mapclass(void);
 
     int intpol(int a, int b, float c);
 
@@ -29,16 +29,16 @@ public:
 
     void settrinket(int x, int y);
 
-    void resetmap();
+    void resetmap(void);
 
-    void resetnames();
+    void resetnames(void);
 
     void transformname(int t);
 
     std::string getglitchname(int x, int y);
 
-    void initmapdata();
-    void initcustommapdata();
+    void initmapdata(void);
+    void initcustommapdata(void);
 
     int finalat(int x, int y);
 
@@ -52,7 +52,7 @@ public:
 
     void updatetowerglow(TowerBG& bg_obj);
 
-    void nexttowercolour();
+    void nexttowercolour(void);
 
     void settowercolour(int t);
 
@@ -65,14 +65,14 @@ public:
 
     int area(int _rx, int _ry);
 
-    void exploretower();
+    void exploretower(void);
 
-    void hideship();
+    void hideship(void);
 
-    void showship();
+    void showship(void);
 
     void resetplayer(const bool player_died);
-    void resetplayer();
+    void resetplayer(void);
 
     void warpto(int rx, int ry , int t, int tx, int ty);
 
@@ -82,7 +82,7 @@ public:
 
     void loadlevel(int rx, int ry);
 
-    void twoframedelayfix();
+    void twoframedelayfix(void);
 
 
     int roomdeaths[20 * 20];