Fix for concatenated headers/line endings

See:
https://forum.textpattern.com/viewtopic.php?pid=333420#p333420
https://forum.textpattern.com/viewtopic.php?pid=335000#p335000
https://forum.textpattern.com/viewtopic.php?pid=335239#p335239

Thanks, hidalgo, Kjeld, Gallex, and phiw13 for reports and testing.

Author: Bloke

com_connect.php

@@ -521,7 +521,14 @@ function com_connect($atts, $thing = '')
             $subject = parse_form($subject_form);
         }
 
-        $sep = IS_WIN ? "\r\n" : "\n";
+        $sep = "\n";
+
+        if (IS_WIN) {
+            $sep = "\r\n";
+        } elseif (ini_get('cgi.rfc2616_headers') != 0) {
+            $sep = "\r\n";
+        }
+
         $msg = array();
         $fields = array();