MDL-70457 forms: php74 fix for the (not used in core) date element

Curly brackets to access by index to strings or arrays is
deprecated since php74.

lib/pear/HTML/QuickForm/date.php

@@ -308,7 +308,7 @@ class HTML_QuickForm_date extends HTML_QuickForm_group
         $locale    =& $this->_locale[$this->_options['language']];
         $backslash =  false;
         for ($i = 0, $length = strlen($this->_options['format']); $i < $length; $i++) {
-            $sign = $this->_options['format']{$i};
+            $sign = $this->_options['format'][$i];
             if ($backslash) {
                 $backslash  = false;
                 $separator .= $sign;
@@ -507,4 +507,4 @@ class HTML_QuickForm_date extends HTML_QuickForm_group
 
     // }}}
 }
-?>
+?>

lib/pear/README_MOODLE.txt

@@ -12,6 +12,10 @@ Quickforms
 Full of our custom hacks, no way to upgrade to latest upstream.
 Most probably we will stop using this library in the future.
 
+Just dropping a couple of links here, for whenever we update/switch or whatever:
+- QF2: https://github.com/pear/HTML_QuickForm2 (https://moodle.org/mod/forum/discuss.php?d=200124)
+- Quickform (fork): https://github.com/openpsa/quickform
+
 MDL-20876 - replaced split() with explode() or preg_split() where appropriate
 MDL-40267 - Moodle core_text strlen functions used for range rule rule to be utf8 safe.
 MDL-46467 - $mform->hardfreeze causes labels to loose their for HTML attribute
@@ -24,6 +28,7 @@ MDL-60281 - replaced deprecated create_function() with lambda functions for PHP7
 MDL-70711 - removed unnecessary if-else conditional block in HTML_QuickForm as the given
             condition always evaluates to false due to the deprecated get_magic_quotes_gpc()
             which always returns false
+MDL-70457 - PHP 7.4 curly brackets string access fix.
 
 Pear
 ====