Add bug in zip_merge noted by Maxim Samsonov.
Add bug in zip_merge noted by Maxim Samsonov.

cysp/libzip,projedi/libzip,cysp/libzip,projedi/libzip,projedi/libzip,cysp/libzip,cysp/libzip,JanX2/libzip-git,projedi/libzip,JanX2/libzip-git