Upgrade from Smarty 3 to Smarty 4 to be PHP 8.1 compatible

Remove all Smarty4 dedicated tests, all are done in the same test file
like before

www/lib/smarty-4.1.0/docs/programmers/smarty-constants.md

@@ -0,0 +1,27 @@
+Constants {#smarty.constants}
+=========
+
+SMARTY\_DIR {#constant.smarty.dir}
+===========
+
+This is the **full system path** to the location of the Smarty class
+files. If this is not defined in your script, then Smarty will attempt
+to determine the appropriate value automatically. If defined, the path
+**must end with a trailing slash/**.
+
+
+    <?php
+    // set path to Smarty directory *nix style
+    define('SMARTY_DIR', '/usr/local/lib/php/Smarty-v.e.r/libs/');
+
+    // path to Smarty windows style
+    define('SMARTY_DIR', 'c:/webroot/libs/Smarty-v.e.r/libs/');
+
+    // include the smarty class, note 'S' is upper case
+    require_once(SMARTY_DIR . 'Smarty.class.php');
+    ?>
+
+         
+
+See also [`$smarty.const`](../designers/language-variables/language-variables-smarty.md) and
+[`$php_handling constants`](./api-variables/variable-php-handling.md)