Simplify the setup-config.php UI flow and load process.

When no configuration file is detected, we now redirect to setup-config.php. This process now uses the WordPress bootstrap, rather than a set of fragile hacks.

fixes #28740.

Built from https://develop.svn.wordpress.org/trunk@28978


git-svn-id: http://core.svn.wordpress.org/trunk@28767 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/wp-db.php

@@ -604,6 +604,11 @@ class wpdb {
 		$this->dbname = $dbname;
 		$this->dbhost = $dbhost;
 
+		// wp-config.php creation will manually connect when ready.
+		if ( defined( 'WP_SETUP_CONFIG' ) ) {
+			return;
+		}
+
 		$this->db_connect();
 	}