Use installing variable (from Donncha)

git-svn-id: http://svn.automattic.com/wordpress/trunk@2455 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/install.php

@@ -1,5 +1,5 @@
 <?php
-$_wp_installing = 1;
+define('WP_INSTALLING', true);
 if (!file_exists('../wp-config.php')) 
     die("There doesn't seem to be a <code>wp-config.php</code> file. I need this before we can get started. Need more help? <a href='http://wordpress.org/docs/faq/#wp-config'>We got it</a>. You can <a href='setup-config.php'>create a <code>wp-config.php</code> file through a web interface</a>, but this doesn't work for all server setups. The safest way is to manually create the file.");
 

wp-admin/setup-config.php

@@ -1,5 +1,5 @@
 <?php
-$_wp_installing = 1;
+define('WP_INSTALLING', true);
 
 if (file_exists('../wp-config.php')) 
 	die("The file 'wp-config.php' already exists. If you need to reset any of the configuration items in this file, please delete it first.");

wp-admin/upgrade.php

@@ -1,5 +1,5 @@
 <?php
-$_wp_installing = 1;
+define('WP_INSTALLING', true);
 if (!file_exists('../wp-config.php')) die("There doesn't seem to be a wp-config.php file. Double check that you updated wp-config-sample.php with the proper database connection information and renamed it to wp-config.php.");
 require('../wp-config.php');
 timer_start();

wp-includes/functions.php

@@ -303,7 +303,7 @@ function url_to_postid($url = '') {
 
 function get_settings($setting) {
   global $wpdb, $cache_settings, $cache_nonexistantoptions;
-	if ( strstr($_SERVER['REQUEST_URI'], 'wp-admin/install.php') )
+	if ( strstr($_SERVER['REQUEST_URI'], 'wp-admin/install.php') || constant('WP_INSTALLING') )
 		return false;
 
 	if ( empty($cache_settings) )