test: statusSpec: do not test for content-range

Content-Range is not among the "simple" headers defined in CORS specification.
Firefox 3.5, Firefox 3.6 and Safari 4.0 does not support
Access-Control-Expose-Headers.
The way to detect support for Access-Control-Expose-Headers is
not yet discovered.
browser: use the xhr.onuploadprogress event handler that is present in Firefox
browser: statuses feature flag: remove 206, 300, 304 for Opera

No version of Opera has been found to support these.