Georgian characters not working on Mac

There seems to be a bug on Mac where it does not list the full language support for certain fonts. For instance, both "Arial Unicode MS" and "Menlo" have Georgian listed as supported in their unicode ranges, but "ka" does not appear in the language set supported by the fonts as reported by Cocoa.

The font matching algorithm in Cocoa, which we used directly in Qt 4, apparently does not use these language tags to decide writing system support, and it does seem like the wrong angle for this. In Qt 5 we actually use the language list to do our own font matching, so on Mac we find no matching font for Mkhedruli text.

We should at least look at the OS/2 table and add any supported script which is missing from the list provided by Cocoa.