Adding appendZip function to PHPZip

* Added: added function appendZip to the Zip classes. This allows the
ser to add pre-compressed static data to the final Zip file, without
having to re-compress this data.

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WARNING: THE CURRENT VERSION OF PHPZip *MAY* FAIL IF THE SERVER HAS
mbstring.func_overload INSTALLED AND ACTIVE!
OLDER VERSIONS OF PHPZip *WILL* FAIL IF THE SERVER HAS
mbstring.func_overload INSTALLED AND ACTIVE!
EXPERIMENTAL FEATURES HAVE BEEN ADDED TO ALLEVIATE THE LOBOTOMIZATION OF
PHP, CAUSED BY mbstring.func_overload

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