New code from lwip project

lwip repo:
4335e99 netconn_gethostbyname() needs to check for name length when LWIP_MPU_COMPATIBLE==1
1fd4b85 Moved #define NETDB_ELEM_SIZE from dns.h to netdb.h, where it belongs, and use sizeof() instead of hacked constants that are wrong on 64-bit platforms
142cc8f minor: fixed a comment typo only
5c37c63 fixed bug #42117 lwip_fcntl does not set errno