I found this in the gcc manpage. It shows all the the recognized c++ extension. Don't worry about this issue if it actually takes coding on your. I was just hoping there might be a way to edit the config file to get "*.C" recognized as c++ code.
I added the extension to the C++ filetype and in a few hours it should be available via CVS.
Probably in the future it will be possible to change the file extensions. But surely not in the next release ;-)