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/charset.md

@@ -0,0 +1,43 @@
+Charset Encoding {#charset}
+================
+
+Charset Encoding {#charset.encoding}
+================
+
+There are a variety of encodings for textual data, ISO-8859-1 (Latin1)
+and UTF-8 being the most popular. Unless specified otherwise with the
+`SMARTY_RESOURCE_CHAR_SET` constant, Smarty recognizes `UTF-8` as the
+internal charset if [Multibyte String](https://www.php.net/mbstring) is
+available, `ISO-8859-1` if not.
+
+> **Note**
+>
+> `ISO-8859-1` has been PHP\'s default internal charset since the
+> beginning. Unicode has been evolving since 1991. Since then it has
+> become the one charset to conquer them all, as it is capable of
+> encoding most of the known characters even accross different character
+> systems (latin, cyrillic, japanese, ...). `UTF-8` is unicode\'s most
+> used encoding, as it allows referencing the thousands of character
+> with the smallest size overhead possible.
+>
+> Since unicode and UTF-8 are very wide spread nowadays, their use is
+> strongly encouraged.
+
+> **Note**
+>
+> Smarty\'s internals and core plugins are truly UTF-8 compatible since
+> Smarty 3.1. To achieve unicode compatibility, the [Multibyte
+> String](https://www.php.net/mbstring) PECL is required. Unless your PHP
+> environment offers this package, Smarty will not be able to offer
+> full-scale UTF-8 compatibility.
+
+
+    // use japanese character encoding
+    if (function_exists('mb_internal_charset')) {
+      mb_internal_charset('EUC-JP');
+    }
+    define('SMARTY_RESOURCE_CHAR_SET', 'EUC-JP');
+    require_once 'libs/Smarty.class.php';
+    $smarty = new Smarty();
+      
+