Remove game.gameframerate as duplicate of game.slowdown

game.gameframerate seems to exist for converting the value of
game.slowdown into an actual timestep value, when really the timestep
value should just use game.slowdown directly with a fast lookup table.
Otherwise, there's a bunch of duplicated game.slowdown case-switches
everywhere, which adds up to a large, annoying pile should the values be
changed in the future. But now the duplicate variable has been removed,
and with it, all the copy-pasted case-switches.

Also, the game speed text rendering in Menu::accessibility and
Menu::setslowdown has been factored out to a function and de-duplicated
as well.

desktop_version/src/main.cpp

@@ -55,6 +55,23 @@ volatile Uint32 accumulator = 0;
 volatile Uint32 f_time = 0;
 volatile Uint32 f_timePrev = 0;
 
+static inline Uint32 get_framerate(const int slowdown)
+{
+    switch (slowdown)
+    {
+    case 30:
+        return 34;
+    case 24:
+        return 41;
+    case 18:
+        return 55;
+    case 12:
+        return 83;
+    }
+
+    return 34;
+}
+
 void inline deltaloop();
 void inline fixedloop();
 
@@ -278,14 +295,6 @@ int main(int argc, char *argv[])
         game.gamestate = TITLEMODE;
     if (game.slowdown == 0) game.slowdown = 30;
 
-    switch(game.slowdown){
-        case 30: game.gameframerate=34; break;
-        case 24: game.gameframerate=41; break;
-        case 18: game.gameframerate=55; break;
-        case 12: game.gameframerate=83; break;
-        default: game.gameframerate=34; break;
-    }
-
     //Check to see if you've already unlocked some achievements here from before the update
     if (game.swnbestrank > 0){
         if(game.swnbestrank >= 1) game.unlockAchievement("vvvvvvsupgrav5");
@@ -413,7 +422,7 @@ void inline deltaloop()
     }
     else if (game.gamestate == GAMEMODE)
     {
-        timesteplimit = game.gameframerate;
+        timesteplimit = get_framerate(game.slowdown);
     }
     else
     {