Signal that extractors need to implement spec version 4.5 (or higher)
for files with sizes of 4GB and more. Older unzippers might produce
truncated results otherwise; they should rather refuse to extract.
Signed-off-by: Rene Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>