Revert collision tweaks #9365 and #9327 (#9591)

This reverts commit df74d36.
This reverts commit 908e762.

Restores the original collision detection bugs to release 5.2.0 prior the large collision detection fix.

src/collision.cpp

@@ -415,12 +415,12 @@ collisionMoveResult collisionMoveSimple(Environment *env, IGameDef *gamedef,
 		Collision uncertainty radius
 		Make it a bit larger than the maximum distance of movement
 	*/
-	//f32 d = pos_max_d * 1.1f;
+	f32 d = pos_max_d * 1.1f;
+	// A fairly large value in here makes moving smoother
+	//f32 d = 0.15*BS;
 
-
-	f32 d = 0.3f;	// Temporary fix, any nonzero d causes collision glitches, the more the greater it is.
-	// ultimately it has to be determined if any uncertainty is involved, and if it is, eliminated
-	// and d & pos_max_d params removed from function calls.
+	// This should always apply, otherwise there are glitches
+	assert(d > pos_max_d);	// invariant
 
 	int loopcount = 0;