Retype testwallsy's tx and ty to be ints, not floats

I have no idea why they were floats in the first place. They are
coordinates, and coordinates are integer positions in this game. They
get converted to float only to be explicitly `static_cast`ed back to
ints in `testwallsy`.

desktop_version/src/Entity.h

@@ -155,7 +155,7 @@ public:
 
     bool testwallsx(int t, int tx, int ty, bool skipdirblocks);
 
-    bool testwallsy(int t, float tx, float ty);
+    bool testwallsy(int t, int tx, int ty);
 
     void applyfriction(int t, float xrate, float yrate);