Digest HTTP authentication

[callcc]

Hi, POCO maintainers and users. Here is my attempt to implement HTTP digest authentication for POCO. It is not ready to be included in the main source tree (only client side, some parts potentially useful for server side are private now, etc), but it is ready to be tested and improved. If you ever needed HTTP digest authentication with POCO, please give it a try.

[guenter]

Thanks. Looks interesting for inclusion in one of the next releases.

[aderouineau]

Thanks! I'm sure this will please quite a few users.