Doxygen has a "pre" command (http://www.stack.nl/~dimitri/doxygen/manual/commands.html#cmdpre) which is not highlighted for C++ source files. Attached is a suggestion to include it.
Thank you for your patch.
However I see no <Keywords name="type2"> tag in langs.model.xml
I guess your patch is based on your (or someone-else) modification.
I see it under <Language name="cpp" ...
It's an old repository.
Please check the new one in :