* The mdns responder has been reworked to lower stack and memory usage. This is
a variation on the upstream code, it use malloc whereas the upstream code uses
pools. The high stack usage of the mdns responder was problem for
esp-open-rtos, so we might have to maintain the differences for now.
* Improved lwip core locking, and lock checking. Upstream improvements, that
need some added support from esp-open-rtos specific code. More core lock is
performed when calling from the esp-open-rtos code now, so a little safer. The
checking is not enforced, but projects might see warning messages and might
want to look into them.
* The esp-open-rtos lwip support has been sync'ed with the new freertos port
included with lwip. There are still some minor differences.
* A few lwip timer bugs have been resolved. This might help resolve some issues.
* Plus it picks up all the other upstream fixes and improvements.
* The default lwip stack has been lowered from 768 words to 480 words,
due to the reduced stack usage by the mdns responder.
Also adds source code for sdk_cnx_rc_search, adding a null pointer dereference
check (that is not expected to be seen), and source code for sdk_cnx_remove_rc.
Function sdk_eagle_auth_done accesses the netif-flags and the NETIF_FLAG_DHCP flag removed in lwip v2, and also the netif->ip_addr so is needed for lwip development.
Function sdk_wpa_config_bss accesses the netif->hwaddr.
Also code for a few other trivial functions that help debug the dhcpc paths.
