Lack of namespace highlighting

I noticed the lack of syntax highlighting support in Qt Creator for namespace names, and decided to tweak things a little bit. The attached diffs adds this enhancement to the C/C++ editor options. The diffs currently set the default to Qt::darkGreen, but I would recommend keeping it to the default text color (or maybe it's TypeUse), so that the existing behavior is unchanged.

It would be great to have this included into the source for Qt Creator, and possibly added to any unit tests that can exercise this functionality.

Thanks!