Wrong ctype definition for UNRARCALLBACK

[davide-romanini]

When integrating on comictagger I found a nasty bug related to the ctype declaration of UNRARCALLBACK on Windows platform.

See comictagger monkey patch for details.
It caused very bad headaches when integrated in a pyinstaller application on win10 64 bit, so maybe it could be fixed directly on the library.

[medoc92]

Hi. Thanks to davide-romanini for fixing this, was pulling my hair.

This is definitely needed for things to work on windows x64 (using python-unrar in Recoll).