Issue #3080: _PyImport_LoadDynamicModule() uses Unicode for name and path

Document also that dynamic module names are ASCII only
diff --git a/Python/importdl.h b/Python/importdl.h
index b4d21be..e51e551 100644
--- a/Python/importdl.h
+++ b/Python/importdl.h
@@ -28,7 +28,7 @@
 extern struct filedescr * _PyImport_Filetab;
 extern const struct filedescr _PyImport_DynLoadFiletab[];
 
-extern PyObject *_PyImport_LoadDynamicModule(char *name, char *pathname,
+extern PyObject *_PyImport_LoadDynamicModule(PyObject *name, PyObject *pathname,
                                              FILE *);
 
 /* Max length of module suffix searched for -- accommodates "module.slb" */