Remove unnecessary intersectRect() function

This function checked the intersection of rectangles, but it used floats
for some reason when its only caller used ints. There's already an
intersection function (UtilityClass::intersects()), so we should be
using that one instead in order to minimize code duplication.

Graphics::Hitest() is used for per-pixel collision detection, directly
checking the pixels of both entities' sprites. I checked with one of my
TASes and it still syncs, so I'm pretty sure this won't cause any
issues.

desktop_version/src/GraphicsUtil.cpp

@@ -501,11 +501,6 @@ void FillRect( SDL_Surface* _surface, SDL_Rect rect, int rgba )
     SDL_FillRect(_surface, &rect, rgba);
 }
 
-bool intersectRect( float left1, float right1, float bottom1, float top1, float left2, float right2, float bottom2, float top2 )
-{
-    return !( left2 > right1 || right2 < left1	|| top2 < bottom1 || bottom2 > top1);
-}
-
 void OverlaySurfaceKeyed( SDL_Surface* _src, SDL_Surface* _dest, Uint32 _key )
 {
     // const SDL_PixelFormat& fmt = *(_src->format);