multithreaded functions are further improved. 

- Available worker slots are limited to 256 ftp worker thread per process.

- It is now possible to pre-set the thread priority of each worker.

- It is now possible to pass a user data (a U++ Value), using Request::UserData() and Result::GetUserData();

- Worker abort mechanism is both simplified and improved.  Vector is ditched in favor of a static Bits instance.
  This reduces both memory consumption and mutex lock/unlock times. Since, previously we needed to iterate over the vector to check if a worker was registered to be aborted.
  This was time consuming. Now we simply set a bit on or off. Since the worker counter resets at 65536 and max. worker slots are limeted to 256, it should be pretty safe.
  See the FtpAsyncIO(), Ftp::AbortWorker() and Ftp::IsWorkerAborted() for details. (I'm open to suggestions, if you have better ideas.) 

- Made room for NetworkProxy support. I will add NetworkProxy support (HTTP/SOCKS4/SOCKS5) via a preprocessor directive (USEPROXY flag), since NetworkProxy package is currently not in bazaar.

- It is now possible to multiselect the files to be downloaded or uploaded.

- FtpBrowser no longer asks for download location for each download. A default download location can be selected. And it can be changed via environment settings.

- FtpBrowser gained file editing support. While it is still a barebone example with ability to edit only one file at a time, it will change in the near future.
  (Mirek had suggested this when we were discussing SSH package last year on "Developer's Corner", which is on it's way, by the way.)
  Of course this is far from what he suggested, but it is operational in it's current state anyway. :)