z64 data descrs are needed when extra data present
z64 data descrs are needed when extra data present

 * If any of original_size, compressed_size, or header_offset must be
   included in the local file header's extra_info (i.e. ZIP64), then the
   data descriptor must follow the z64 format.

Johnetordoff/waterbutler,TomBaxter/waterbutler,RCOSDP/waterbutler,rdhyee/waterbutler,felliott/waterbutler,CenterForOpenScience/waterbutler