Revert "Add a Lua call to do damages / heals" ok @ShadowNinja

This reverts commit 467fc0ddc9.

src/script/lua_api/l_object.h

@@ -83,12 +83,6 @@ private:
 	// 0 if not applicable to this type of object
 	static int l_get_hp(lua_State *L);
 
-	// apply_damage(self, damage)
-	// damage = amount of damage to apply
-	// if damage is negative, heal the player
-	// returns: nil
-	static int l_apply_damage(lua_State *L);
-
 	// get_inventory(self)
 	static int l_get_inventory(lua_State *L);