extmod/modurandom: Add init method to seed the Yasmarang generator.

In CPython the random module is seeded differently on each import, and so
this new macro option MICROPY_PY_URANDOM_SEED_INIT_FUNC allows to implement
such a behaviour.

extmod/modurandom.c

@@ -200,8 +200,19 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_urandom_uniform_obj, mod_urandom_uniform);
 
 #endif // MICROPY_PY_URANDOM_EXTRA_FUNCS
 
+#ifdef MICROPY_PY_URANDOM_SEED_INIT_FUNC
+STATIC mp_obj_t mod_urandom___init__() {
+    mod_urandom_seed(MP_OBJ_NEW_SMALL_INT(MICROPY_PY_URANDOM_SEED_INIT_FUNC));
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_0(mod_urandom___init___obj, mod_urandom___init__);
+#endif
+
 STATIC const mp_rom_map_elem_t mp_module_urandom_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_urandom) },
+    #ifdef MICROPY_PY_URANDOM_SEED_INIT_FUNC
+    { MP_ROM_QSTR(MP_QSTR___init__), MP_ROM_PTR(&mod_urandom___init___obj) },
+    #endif
     { MP_ROM_QSTR(MP_QSTR_getrandbits), MP_ROM_PTR(&mod_urandom_getrandbits_obj) },
     { MP_ROM_QSTR(MP_QSTR_seed), MP_ROM_PTR(&mod_urandom_seed_obj) },
     #if MICROPY_PY_URANDOM_EXTRA_FUNCS