WinZIP AES changes

[Dieter Baron <dillo%nih.at@localhost>]

hi,

we’ve removed the custom AES implementation and instead rely on standard 
cryptographic libraries.

(The version we used was several years old, and the new version isn’t backwards 
compatible. Instead of adapting to a new proprietary API, we preferred to 
switch to standard APIs and use maintained and audited implementations.)

So far we support OpenSSL, GnuTLS and Apple’s native library (CommonCrypto).

We would like to also support the Windows native libraries. Volunteers for 
writing the compatibility layer would be welcome. It should be doable in about 
an hour. zip_random() has also been moved to the crypto backends, since most 
libraries implement it. The Windows versions were removed from the build, but 
the files are still there for reference.

If no supported library can be found, libzip will still build, it just won’t be 
able to read/write WinzipAES encrypted files.

yours,
dillo