[wp-xmlrpc] WP 2.2.1 breaks Ruby 1.8.2

[Joe Cheng]

> Because several popular XML-RPC parsing libraries will choke on the Z

Sorry, I realized I should explain exactly what I mean by this.

Many/most XML-RPC libraries will save you the trouble of parsing the textual values that appear in XML-RPC requests/responses--instead they will use the inlined type tags to convert the text into natively typed values. So even if we add a never-before-used date/time field to MetaWeblog, just the fact that it's a date/time field means the XML-RPC library will attempt to parse it for you and probably fail (often loudly) if the format is not what it was expecting.