New GZip inflater using built-in gzip inflation

Based on David Anson's work here: http://blogs.msdn.com/b/delay/archive/2012/04/19/quot-if-i-have-seen-further-it-is-by-standing-on-the-shoulders-of-giants-quot-an-alternate-implementation-of-http-gzip-decompression-for-windows-phone.aspx