Modified show_error() to allow sending of HTTP server response codes.

Added set_status_header() to the Common functions to allow use when the Output class is unavailable.

Fixed a bug where the 400 status header sent with the 'disallowed URI characters' was not compatible with CGI environments.
diff --git a/system/libraries/Exceptions.php b/system/libraries/Exceptions.php
index 902b574..1f99d01 100644
--- a/system/libraries/Exceptions.php
+++ b/system/libraries/Exceptions.php
@@ -113,8 +113,10 @@
 	 * @param	string	the template name
 	 * @return	string
 	 */
-	function show_error($heading, $message, $template = 'error_general')
+	function show_error($heading, $message, $template = 'error_general', $status_code = 500)
 	{
+		set_status_header($status_code);
+		
 		$message = '<p>'.implode('</p><p>', ( ! is_array($message)) ? array($message) : $message).'</p>';
 
 		if (ob_get_level() > $this->ob_level + 1)