Store real number of records in regular end record when possible

Only store uintmax for the number of entries in the regular end record
if it doesn't fit.  p7zip 16.02 rejects zip files where the number of
entries in the regular end record is larger than the number of entries
counted in the central directory.

Fixes: 187485108
Test: TestZip64P7ZipRecords
Change-Id: I0d116e228a0ee26e4e95bb3f35771da236a056eb