Create _Py_fopen() for PyUnicodeObject path

Call _wfopen() on Windows, or fopen() otherwise. Return the new file object on
success, or NULL if the file cannot be open or (if PyErr_Occurred()) on unicode
error.
diff --git a/Include/Python.h b/Include/Python.h
index eb5ea28..5afde02 100644
--- a/Include/Python.h
+++ b/Include/Python.h
@@ -135,7 +135,8 @@
 PyAPI_FUNC(char*) _Py_wchar2char(const wchar_t *text);
 PyAPI_FUNC(FILE *) _Py_wfopen(const wchar_t *path, const wchar_t *mode);
 
-/* _Py_stat lives in import.c */
+/* These functions live in import.c */
+PyAPI_FUNC(FILE*) _Py_fopen(PyObject *unicode, const char *mode);
 #ifdef HAVE_STAT
 int _Py_stat(PyObject *unicode, struct stat *statbuf);
 #endif