1. Rebind the UDP pcb, which originally bind to non-zero IPv4 address, to
the new IPv4 address when the IPv4 address of related netif is changed.
2. Rebind the TCP pcb, which is in listening status, to the new IPv4 address
when IPv4 address of related netif is changed.
Notice: Recompile some related libs due to netif.h changed.
internal: f194dd34
1. add spi flash erase protect mechanism, boot and current runing user
bin can not been erased;
2. add memleak debug feature;
3. fix spi overlap issue;
4. fix call wifi_station_disconnect, disconnect event enter twice
issue;
5. fix crash when set opmode from station to softAP in scan done
callback;
6. modify spi flash erase/write flow, clear protect status if needed;
7. fix rf init data sector broken issue, add user_rf_cal_sector_set,
user application MUST have this function, refer to examples;
8. fix system parameter sector broken issue when frequently power
on/off;
9. fix the max value of os_timer_arm;
10. fix dns issue in some routers;
11. add sntp support;
12. update smartconfig to 2.5.4;
13. update open freedom to support send beacon packet;
14. fix seldom rf not work issue after external reset;
15. fix pwm issue;
16. fix status error got by wifi_station_get_connect_status;
17. fix assert in pp;
18. fix huawei X4 connect softAP issue;
19. optimize sleep strategy；
20. add vendor IE support;
21. update libphy.a to 1055;
22. add weak function wifi_set_backup_mac to let user set MAC;
23. fix bug of lwip and optimize socket mechanism;
24. update boot loader to v1.6;
25. update esp_init_data_default.bin
26. add mbedtls support；
27. fix other bugs;
