package/zziplib: fix CVE-2018-17828

Directory traversal vulnerability in ZZIPlib 0.13.69 allows attackers to
overwrite arbitrary files via a .. (dot dot) in a zip file, because of
the function unzzip_cat in the bins/unzzipcat-mem.c file.

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>