[Qt-creator] Extend Qt-creator to recognize source file extension .xc

[Coda Highland]

> If the XML file wouldn't be embedded, one could easily adopt it without
> recompiling. Is it worth to add this on the wishlist in your bug tracker?

Better, I think, would be to have a second XML file (in /usr/share or
something) in the same format that would get parsed after the one in
the resources, to allow a comfortable set of defaults while allowing
user customizability.

/s/ Adam