Support for filenames with 'special' characters

A (local) filename that contains characters other than ASCII 32-126 like '/tmp/maïs.jpg' was processed as being binary data, since the [check for printable characters](http://www.php.net/manual/en/function.ctype-print.php) in isBinary() failed.

In the [extended ASCII table](http://www.asciitable.com/), we can see that this excludes a lot of characters that 'can' occur in a filename.