sockets.c: fixed bug #25051: lwip_recvfrom problem with udp: fromaddr and port uses deleted netbuf.
patch #6699: fixed some warnings on platform where sizeof(int) == 2
Another fix for bug #6683 (and a typo in changelog)
Reverted last changes since it's wrong when sizeof(int)==2...
* pbuf.c: reclaim pbufs from TCP out-of-sequence segments if we run
  out of pool pbufs.
  * ipv4/inet_chksum.c, ipv4/lwip/inet_chksum.h: inet_chksum_pseudo_partial()
  is only used by UDPLITE at present, so conditionalise it.
fixed bug #25467: Listen backlog is not reset on timeout in SYN_RCVD: Accepts_pending is decrease on a corresponding listen pcb when a connection in state SYN_RCVD is close.
Moved INADDR_* defines to inet.h; removing dependency from inet.h to ip_addr.h
Fixed bug #25544: DHCP_COARSE_TIMER_MSECS could overflow on 16-bit targets
added configurable default valud for netconn->recv_bufsize: RECV_BUFSIZE_DEFAULT (fixes bug #23726: pbuf pool exhaustion on slow recv())
including inet.h because htonl is used
fixed bug #24480 (releasing old udp_pdb and pbuf in dhcp_start)
added MEMP_MEM_MALLOC to use mem_malloc/mem_free instead of the pool allocator (can save code size with MEM_LIBC_MALLOC if libc-malloc is otherwise used)
fixed bug #25345 (DHCPDECLINE is sent with "Maximum message size" option)
Added LWIP_VERSION to get the current version of the stack (implements task #9032: Provide means to get Version of Stack and submodules)
LWIP_VERSION: corrected shifting for 16-bit platforms, added LWIP_RC_DEVELOPMENT
Fixed compilation error in LWIP_VERSION
fixed bug #24440: TCP connection close problem on 64-bit host by moving accept callback function pointer to TCP_PCB_COMMON
fixed arguments of socket functions to match the standard; converted size argument of netconn_write to 'size_t' for that; fixed some warnings
patch #6539: (configurable) response to broadcast- and multicast pings