Check if unzip supports the ZIP64 format and skip the tests that create
big archives otherwise. Also skip the test that archives a big file on
32-bit platforms because the git object systems can't unpack files
bigger than 4GB there.
Reported-by: Torsten Bögershausen <tboegi@web.de> Signed-off-by: Rene Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>