Pointer tcpip_api_call *m should be converted to pppapi_msg* instead of pppapi_msg_msg*
in pppapi_do_ppp_set_default(), pppapi_do_ppp_free() and so on.
It solve this issue https://github.com/espressif/esp-idf/pull/1028
so there is no need to patch ip4.c because now netif_defauilt is setted correctly.
Also it prevents memory corruption when pppapi_free() is called.