PHP7.2 Patch bennu library for PHP 7.2. compatibility

diff --git a/lib/bennu/iCalendar_properties.php b/lib/bennu/iCalendar_properties.php

index 260c42a..6a7a562 100644

--- a/lib/bennu/iCalendar_properties.php

+++ b/lib/bennu/iCalendar_properties.php

@@ -107,7 +107,10 @@ class iCalendar_property {

         $valarray = explode('\\,', $this->value);

         // Undo transparent formatting

-        $replace_function = create_function('$a', 'return rfc2445_undo_value_formatting($a, '.$this->val_type.');');

+        $valtype = $this->val_type;

+        $replace_function = function($a) use ($valtype) {

+            return rfc2445_undo_value_formatting($a, $valtype);

+        };

         $valarray = array_map($replace_function, $valarray);

         // Now, if this property cannot have multiple values, don't return as an array