forwardbody option for redirects

[ghazel]

This is a feature request for a forwardbody type of feature for redirects, much like the forwardheaders option. Simply put, POST data would get re-submitted after a redirect. This plus redirect_method=:same would be roughly equivalent to curl's --post301 option.

From curl:

--post301 Tells curl to respect RFC 2616/10.3.2 and not convert POST requests into GET requests when following a 301 redirection. The non-RFC behaviour is ubiquitous in web browsers, so curl does the conversion by default to maintain consistency.