Winzip AES support committed

[Thomas Klausner <tk%giga.or.at@localhost>]

Hi!

We've just committed support for Winzip AES encryption. This is the
AES encryption version that's supported by 7zip and Winzip.

Use the new function zip_file_set_encryption() to encrypt files, and
zip_fopen_encrypted() for decrypting files. You can also provide an
archive-wide password with zip_set_password() for both encryption and
decryption.

Windows support is missing a part for encryption: Can someone please
fill in lib/zip_random_windows.c with code to provide random bytes?

Let us know if you find any problems.

Cheers,
 Thomas & Dillo