The cython plugin doesn't like parent class with no default constructor

The cython plugin doesn't seem to handle classes parent classes without default constructors.

```
Error compiling Cython file:
------------------------------------------------------------
...

cdef extern from "basics.h" namespace "cppproj":

    cdef cppclass NoDefaultChild(NoDefault):
        # constructors
        NoDefaultChild(int) except +
                      ^
------------------------------------------------------------

/home/tewk/xdress3/tests/cppproj/cppproj/cpp_basics.pxd:237:23: no matching function for call to NoDefault::NoDefault()
```