Code Modernization: Use explicit visibility for class property declarations.

Using `var` or only `static` to declare a class property is PHP 4 code.

This updates the codebase to use explicit visibility modifiers introduced in PHP 5.

Props jrf.
Fixes #51557. See #22234.

git-svn-id: https://develop.svn.wordpress.org/trunk@49184 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/tests/multisite/wpMSSitesListTable.php

@@ -12,7 +12,7 @@ if ( is_multisite() ) :
 		/**
 		 * @var WP_MS_Sites_List_Table
 		 */
-		var $table = false;
+		public $table = false;
 
 		function setUp() {
 			parent::setUp();