Define WPINC in wp-load when wp-config does not exist. see #19651.

git-svn-id: http://core.svn.wordpress.org/trunk@19633 1a063a9b-81f0-0310-95a4-ce76da25c4cd

Author: nacin

wp-load.php

@@ -46,6 +46,7 @@
 	require_once( ABSPATH . '/wp-includes/load.php' );
 	require_once( ABSPATH . '/wp-includes/version.php' );
 	define( 'WP_CONTENT_DIR', ABSPATH . 'wp-content' );
+	define( 'WPINC', 'wp-includes' );
 	wp_check_php_mysql_versions();
 
 	// Die with an error message