Issue #29083: Fixed the declaration of some public API functions.
PyArg_VaParse() and PyArg_VaParseTupleAndKeywords() were not available in
limited API.  PyArg_ValidateKeywordArguments(), PyArg_UnpackTuple() and
Py_BuildValue() were not available in limited API of version < 3.3 when
PY_SSIZE_T_CLEAN is defined.