Add support for 451 http status code (Unavailable For Legal Reasons.)

Though this is technically still in the proposal stage, there is support from the core team and precedent in #16914

Props andizer.
Fixes #35333.

Built from https://develop.svn.wordpress.org/trunk@36273


git-svn-id: http://core.svn.wordpress.org/trunk@36240 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/functions.php

@@ -1021,6 +1021,7 @@ function get_status_header_desc( $code ) {
 			428 => 'Precondition Required',
 			429 => 'Too Many Requests',
 			431 => 'Request Header Fields Too Large',
+			451 => 'Unavailable For Legal Reasons',
 
 			500 => 'Internal Server Error',
 			501 => 'Not Implemented',

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.5-alpha-36272';
+$wp_version = '4.5-alpha-36273';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.