Merge branch 'PHP-7.4'

* PHP-7.4:
  - bump zip extension version to 1.15.6 - add ZipArchive::LIBZIP_VERSION - skip bug53885.phpt with libzip 1.6.0 (empty file is no more valid archive)

diff --cc ext/zip/php_zip.c
Simple merge

diff --cc ext/zip/php_zip.h
Simple merge