* Moved the code for creating and parsing the gzip extra field into
IO::Compress::Zlib::Extra.pm so that IO::Compress::Zip &
IO::Uncompress::Unzip can use it as well.
* Added ExtraFieldLocal & ExtraFieldCentral options to IO::Compress::Zip.
These allow the creation of user-defined extra fields in the local
and central headers, just like the ExtraField option in
IO::Compress::Gzip.
* Moved the zip constants into IO::Compress::Zip::Constants
* Added exTime option to IO::Compress::Zip.
This allows creation of the extended timestamp extra field.
* Added Minimal option to IO::Compress::Zip.
This disables the creation of all extended fields.
* Added TextFlag option to IO::Compress::Zip.
* Documented Comment and ZipComment options in IO::Compress::Zip.