Handle HTTP request body params better.

See [PEAR Bug 17806](https://pear.php.net/bugs/bug.php?id=17806)

[RFC 5849 section 3.4.1.3.1](http://tools.ietf.org/html/rfc5849#section-3.4.1.3.1) says any request can have params in the request body provided the content-type is set correctly and the entity-body is single-part and formatted correctly.