Values in ZIP files are unsigned.
Ported to 4.2 from:
https://android.googlesource.com/platform/libcore/+/9edf43dfcc35c761d97eb9156ac4254152ddbc55%5E%21/#F1
Remove support for duplicate file entries
Bug: 8219321
Change-Id: Ibc56bea753917c38e1bb20df48aa45fdff39d364

From https://github.com/CyanogenMod/android_libcore/commit/fe70e697810a7a8b9ce47325f53d16fdbc19f1f8