Update mime types of various powerpoint extensions.

Fixes #3121

lib/Cake/Network/CakeResponse.php

@@ -131,10 +131,10 @@ class CakeResponse {
 		'otf' => 'font/otf',
 		'pdf' => 'application/pdf',
 		'pgn' => 'application/x-chess-pgn',
-		'pot' => 'application/mspowerpoint',
-		'pps' => 'application/mspowerpoint',
-		'ppt' => 'application/mspowerpoint',
-		'ppz' => 'application/mspowerpoint',
+		'pot' => 'application/vnd.ms-powerpoint',
+		'pps' => 'application/vnd.ms-powerpoint',
+		'ppt' => 'application/vnd.ms-powerpoint',
+		'ppz' => 'application/vnd.ms-powerpoint',
 		'pre' => 'application/x-freelance',
 		'prt' => 'application/pro_eng',
 		'ps' => 'application/postscript',