Small fixes for Unzip to be compatible AES versions 1 and 2 

Please review these changes and refer to http://www.winzip.com/win/fr/aes_info.html

The original version didn't allow for AE-2 zip files created by 7zip even though they could be read, they were excluded. Also, the AE-1 version that was implemented was not testing the CRC32 even though according to the URL above AE-1 expects a valid CRC32.

Please accept this contribution under the same terms in which I received it. If any of my changes are defective, please correct or rewrite as it seems appropriate. Thank you.