Add support for dpi based HUD scaling

Add support for (configurable) multiline hotbar
Improved screensize handling
Add userdefined gui scale by BlockMen

src/script/lua_api/l_mainmenu.h

@@ -103,6 +103,8 @@ private:
 
 	static int l_update_formspec(lua_State *L);
 
+	static int l_get_screen_info(lua_State *L);
+
 	//filesystem
 
 	static int l_get_scriptdir(lua_State *L);