Multisite: Change WP_Network id property to an integer.

For consistency and developer sanity.

Props flixos90.
Fixes #37050.

Built from https://develop.svn.wordpress.org/trunk@37870


git-svn-id: http://core.svn.wordpress.org/trunk@37811 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/pluggable.php

@@ -1127,6 +1127,19 @@ if ( !function_exists('wp_redirect') ) :
 /**
  * Redirects to another page.
  *
+ * Note: wp_redirect() does not exit automatically, and should almost always be
+ * followed by a call to `exit;`:
+ *
+ *     wp_redirect( $url );
+ *     exit;
+ *
+ * Exiting can also be selectively manipulated by using wp_redirect() as a conditional
+ * in conjunction with the {@see 'wp_redirect'} and {@see 'wp_redirect_location'} hooks:
+ *
+ *     if ( wp_redirect( $url ) {
+ *         exit;
+ *     }
+ *
  * @since 1.5.1
  *
  * @global bool $is_IIS