Introduce wp_get_db_schema() for rerieving the various flavors of the WP db schema. Eliminates need to use global. Allows multiple calls to wpmu_create_blog(). see #12028

git-svn-id: https://develop.svn.wordpress.org/trunk@18899 602fd350-edb4-49c9-b593-d223f7449a82

wp-admin/network.php

@@ -10,7 +10,7 @@
  * @subpackage Administration
  */
 
-define( 'WP_NETWORK_ADMIN_PAGE', true );
+define( 'WP_INSTALLING_NETWORK', true );
 
 /** WordPress Administration Bootstrap */
 require_once( './admin.php' );