I managed to get the .hh files recognized as C++ header files by Xcode. So question answered.
Nice! The comment about using the issue handling of github is that it better supports dialog. This is often lost if a new topic is not created on the forum. Also after time the topics often become multi-purpose.
It does not have to be a trouble report for an issue. I like to use it also for new features, discussing design, etc. As the issue tracking is integrated with github there is a lot of benefits such as linking to commits, lines of code, other issues, etc. But the most important is keeping the dialog intact and you get attention ;-)
Appreciate your efforts!
[Update: Link to issue on github, https://github.com/mikaelpatel/Cosa/issues/146