Fix CppParser compile warnings

These fix three (kind of) trivial compile warnings. Only "kind of" as it's rather difficult to come up with good names for those variables that would not clash with the type names.

I also considered getters & setters + private variables, but I didn't want to start changing too much code at this point.

After these I get a clean build of CppParser on Linux, although enabling -Wall and -Wextra will give lots of more warnings. But at least all the major warnings are gone, and we no longer need -fpermissive flag.