Squashed commit of the following:

commit 5935a362c75ecef04d5ec9775cbcaf2165921e8d
Author: Andrew Plummer <plummer.andrew@gmail.com>
Date:   Fri Feb 1 02:40:42 2013 +0900

    Using "hasOwnProperty" to check for direct properties "type" and
    "namespace" on events before triggering.

Change uglify-js options for compressor
Change variables initialization sequence for some declarations

(Cherry picked from a6c358d0)

Also migrates the XHR check added to 2.0 in 62acda81.

Ignore file inputs when serializing forms. File input serialization is handled by plugins. Fixes #13306.

Never use the XML as parsed by the XHR instance. Use raw text instead and let the ajax conversion logic do the trick. -20 min/gzipped. Fixes #13276. Unit test added.

(cherry picked from commit 50290b8f)

(cherry picked from commit cc324abf)

(cherry picked from commit 31b95797)