Fix error `Function create_function() is deprecated `with PHP 7.2

Replace these two lines

	// Start this plugin once all other plugins are fully loaded
	add_action( 'plugins_loaded', create_function('', '$memory = new wp_memory_usage();') );

with

	// Start this plugin once all other plugins are fully loaded
	//add_action( 'plugins_loaded', create_function('', '$memory = new wp_memory_usage();') );
	add_action( 'plugins_loaded', function () { return $memory = new wp_memory_usage();}, 10);