Change default date format

This change stems from the fact that date('T') on PHP 4 (and possibly 5.0/5.1/etc) returns "Central Daylight Time" vs PHP 5, which returns "CDT".  "CDT" is parsable by strtotime - "Central Daylight Time" is not.

There will still be some dates that won't properly decode, however, on PHP 4.  Those dates would seem to be due to this (from php.net):

"On systems where time_t is a 32bit signed integer, as most common today, the valid range for year is somewhere between 1901 and 2038. However, before PHP 5.1.0 this range was limited from 1970 to 2038 on some systems (e.g. Windows)."

phpseclib/File/ASN1.php

@@ -167,11 +167,11 @@ class File_ASN1 {
     /**
      * Default date format
      *
-     * @var Array
+     * @var String
      * @access private
      * @link http://php.net/class.datetime
      */
-    var $format = 'M j H:i:s Y T';
+    var $format = 'D, d M y H:i:s O';
 
     /**
      * Default date format