Remove clamp in favor of SDL_clamp

For the same reasons as I removed VVV_min/max in favor of SDL_min/max in
aa7b63fa5f, I'm doing the same thing here.

desktop_version/src/Editor.cpp

@@ -2306,8 +2306,8 @@ void editorinput(void)
                     break;
                 }
 
-                ed.levx = clamp(help.Int(coord_x) - 1, 0, cl.mapwidth - 1);
-                ed.levy = clamp(help.Int(coord_y) - 1, 0, cl.mapheight - 1);
+                ed.levx = SDL_clamp(help.Int(coord_x) - 1, 0, cl.mapwidth - 1);
+                ed.levy = SDL_clamp(help.Int(coord_y) - 1, 0, cl.mapheight - 1);
                 graphics.backgrounddrawn = false;
                 break;
             }

desktop_version/src/Graphics.cpp

@@ -521,10 +521,10 @@ void Graphics::do_print(
     int position = 0;
     std::string::const_iterator iter = text.begin();
 
-    r = clamp(r, 0, 255);
-    g = clamp(g, 0, 255);
-    b = clamp(b, 0, 255);
-    a = clamp(a, 0, 255);
+    r = SDL_clamp(r, 0, 255);
+    g = SDL_clamp(g, 0, 255);
+    b = SDL_clamp(b, 0, 255);
+    a = SDL_clamp(a, 0, 255);
 
     ct.colour = getRGBA(r, g, b, a);
 

desktop_version/src/Input.cpp

@@ -356,7 +356,7 @@ static void slidermodeinput(void)
     {
         *user_changing_volume += USER_VOLUME_STEP;
     }
-    *user_changing_volume = clamp(*user_changing_volume, 0, USER_VOLUME_MAX);
+    *user_changing_volume = SDL_clamp(*user_changing_volume, 0, USER_VOLUME_MAX);
 }
 
 static void menuactionpress(void)

desktop_version/src/Maths.h

@@ -13,11 +13,6 @@ float inline fRandom(void)
     return ( float(rand()) / float(RAND_MAX)) ;
 }
 
-inline int clamp(int x, int a, int b)
-{
-    return x < a ? a : (x > b ? b : x);
-}
-
 struct point
 {
     int x;

desktop_version/src/Render.cpp

@@ -78,7 +78,7 @@ static void volumesliderrender(void)
     num_positions = slider_length - symbol_length + 1;
 
     offset = num_positions * (*volume_ptr) / USER_VOLUME_MAX;
-    offset = clamp(offset, 0, slider_length - symbol_length);
+    offset = SDL_clamp(offset, 0, slider_length - symbol_length);
 
     /* SDL_strlcpy null-terminates, which would end the string in the middle of
      * it, which we don't want!