PAX Extract file fix Pull#2

[ovidiul]

[splitbrain]

Looking at the IBM document you provided in #18 an x header will contain key value pairs. I dumped the header from your files and that confirms it:

28 path=./4слайд.jpg
20 ctime=1489408528
20 atime=1489408285
23 SCHILY.dev=16777220
23 SCHILY.ino=53836974
18 SCHILY.nlink=1

So for implementing it correctly, the path key in this header should overwrite the filename from the standard header.

The header may also contain a charset key which would give all other data (including path) in that charset. We would probably need to call iconv or mbstring on that then.

Ideally we should also create such a header when adding UTF-8 filenames.