MSIE attachment download problem fixed!

[Guenther Blatzheim]

Unfortunatly we made the same bad experiences with attachment downloads 
using MSIE. Version 4 or 5.x doesn't matter. Netscape was fine in any version.

The problem is cause by the cache control headers ("no-cache" / "no-store") 
in the download page.

Solution: In /cgi/cginocache.c change "no-cache" -> "private" and 
"no-store" -> "private".

After recompiling even MSIE downloads should work correct. Tested with 
sqwebmail-1.0

--Guenther