Log Message:
mail/squirrelmail: update to 1.4.23pre14904

Update squirrelmail to 1.4.23pre14904, latest snapshot.

1.4.23pre revision 14904 (2021-03-13)

 - Added the ability to modify of the value of the global $PHP_SELF
   variable used throughout the SquirrelMail code.  The administrator
   may do so by adding the configuration settings $php_self_pattern
   and $php_self_replacement to config/config_local.php, where the
   pattern should be a full regular expression including the
   delimiters. This may be helpful when the web server sees traffic
   from a proxy so the normal $PHP_SELF does not resolve to what it
   should be for the real client.
 - Users can now mouse over the checkbox on the message list to see
   who a message is from
 - Show more accurate filesize for uploaded files and base64-encoded
   attachments (when reading a message)
 - Migrate away from create_function() as long as we have PHP 5.3+