Fix parsing typedefs to size_t (C and C++) or wchar_t (C)

In C and C++, `size_t` is *not* a keyword.  Same goes for `wchar_t` in C.  Having the C and C++ parser erroneously recognize them as keywords prevents it from recognizing typedefs defining them, which leads to them being missing from e.g. *c99.tags*.

So, don't recognize those as keywords as appropriate.

This should not cause any breakage, but as *c.c* is easy to break I'd appreciate more testing.