BUrl: add a Redirect method

* This takes a relative path as a parameter, and modifies the object to
point to the given location.
 * '..' is not handled yet, and will be sent as-is to the server.
 * Makes it possible to follow more types of 302 redirects

In particular, I can now run the tests from Opera's testsuite
(testsuite.opera.com), which shows I have more work to do on cookie
handling.

headers/os/net/Url.h

@@ -29,6 +29,7 @@ public:
 			BUrl&				SetPath(const BString& path);
 			BUrl&				SetRequest(const BString& request);
 			BUrl&				SetFragment(const BString& fragment);
+			void				Redirect(const BString& newLocation);
 			
 	// URL fields access
 			const BString&		UrlString() const;