Opcache issue: opcache.file_cache_callback (or documentation issue?)

Hello togehter,

many people seem to have problems with opcache on windows.

https://bugs.php.net/bug.php?id=70022
http://stackoverflow.com/questions/35908029/zend-opcache-issue-windows-server-2012-iis-plesk-php-7
https://github.com/zendtech/ZendOptimizerPlus/issues/167

My message currently was:
Base address marks unusable memory region. Please setup opcache.file_cache
and opcache.file_cache_callback directives for more convenient Opcache usage
Attempt to access invalid address.

I found the "opcache.file_cache" option and set it to, which seem to fixed
my problem for now.

But what is the option "opcache.file_cache_callback"? I found this option
only there

https://github.com/php/php-src/blob/3d3f11ede4cc7c83d64cc5edaae7c29ce9c6986f/ext/opcache/shared_alloc_win32.c#L189

Best regards
Martin