Upgrade pclzip (#26)

* Sync pclzip with chamilo/pclzip:2.8.4

https://github.com/chamilo/pclzip

* Add back replacing php_uname() with PHP_OS

Ref: 1c7ad96

* Sync pclzip readme.txt with chamilo/pclzip:2.8.4

https://github.com/chamilo/pclzip

* Add back PHP 7 fix for integers

Ref: #9

* Add back ignoring touch failure

* Add back the possibility to define a callable for `PCLZIP_CB_PRE_EXTRACT` instead of a function name

Ref: https://github.com/matomo-org/component-decompress/pull/5/files#diff-3816f6393a3538d218dd07cd1be1cc787a84e5ab48554fee694e4958e7681930R1720

* More documentation