Add being able to toggle over/fixed-30-FPS, off by default

There is now an option in "graphic options" named "toggle fps", which
toggles whether the game visually runs at 1000/34 FPS or over 1000/34
FPS. It is off by default.

I've had to put the entire game loop in yet another set of braces, I'll
indent it next commit.

desktop_version/src/main.cpp

@@ -306,12 +306,34 @@ int main(int argc, char *argv[])
     volatile Uint32 time = 0;
     volatile Uint32 timePrev = 0;
     volatile Uint32 accumulator = 0;
+    volatile Uint32 f_time = 0;
+    volatile Uint32 f_timePrev = 0;
+    volatile Uint32 f_accumulator = 0;
     game.infocus = true;
     key.isActive = true;
     game.gametimer = 0;
 
     while(!key.quitProgram)
     {
+        f_timePrev = f_time;
+        f_time = SDL_GetTicks();
+        const float f_rawdeltatime = static_cast<float>(f_time - f_timePrev);
+        if (!game.over30mode)
+        {
+            f_accumulator += f_rawdeltatime;
+        }
+
+        while ((game.over30mode || f_accumulator >= 34) && !key.quitProgram)
+        {
+            if (game.over30mode)
+            {
+                f_accumulator = 0;
+            }
+            else
+            {
+                f_accumulator = fmodf(f_accumulator, 34);
+            }
+
         timePrev = time;
         time = SDL_GetTicks();
 
@@ -601,6 +623,7 @@ int main(int argc, char *argv[])
             }
             gameScreen.FlipScreen();
         }
+        }
     }
 
     game.savestats();