c, c++: Don't parse size_t as a keyword

This fixes handling of typedefs defining this name.
c: Don't parse wchar_t as a keyword
c: Add a test case for size_t and wchar_t handling
d: size_t and wchar_t aren't keywords in D
Merge PR#393 from 'c/keyword-types'

Fix parsing typedefs to size_t (C/C++/D) and wchar_t (C/D).