extractMember( $memberOrName [, $extractedName ] )
     Extract the given member, or match its name and extract it. Returns
     undef if member doesn't exist in this Zip. If optional second arg is
     given, use it as the name of the extracted member. Otherwise, the
     internal filename of the member is used as the name of the extracted
     file or directory. If you pass $extractedName, it should be in the
     local file system's format. All necessary directories will be
     created. Returns "AZ_OK" on success.