Sockets: Unit tests and apps corrections

* Include lwip/inet.h in some unit tests and apps
  * Since they use htons() and pals.
* test/unit/api/test_sockets.c:
  * write() could be declared by external socket headers
    * Call lwip_write() instead.
  * Code expects fcntl() to return 6
    * But O_RDWR could have another value if external
      socket headers are present
    * Replace 6 by O_RDWR.
* apps/tftp/tftp.c:
  * recv() could be declared by external socket headers
    * Rename it to tftp_recv()

test/unit/api/test_sockets.c

@@ -153,7 +153,7 @@ static void test_sockets_allfunctions_basic_domain(int domain)
   fail_unless(errno == EISCONN);
 
   /* write from server to client */
-  ret = write(s3, "test", 4);
+  ret = lwip_write(s3, "test", 4);
   fail_unless(ret == 4);
 
   ret = lwip_shutdown(s3, SHUT_WR);
@@ -330,7 +330,7 @@ static void test_sockets_msgapi_tcp(int domain)
 
   /* set s2 to non-blocking, not inherited from listener */
   opt = lwip_fcntl(s2, F_GETFL, 0);
-  fail_unless(opt == 6);
+  fail_unless(opt == O_RDWR);
   opt = O_NONBLOCK;
   ret = lwip_fcntl(s2, F_SETFL, opt);
   fail_unless(ret == 0);

test/unit/dhcp/test_dhcp.c

@@ -4,6 +4,7 @@
 #include "lwip/dhcp.h"
 #include "lwip/prot/dhcp.h"
 #include "lwip/etharp.h"
+#include "lwip/inet.h"
 #include "netif/ethernet.h"
 
 #if LWIP_ACD

test/unit/etharp/test_etharp.c

@@ -2,6 +2,7 @@
 
 #include "lwip/udp.h"
 #include "lwip/etharp.h"
+#include "lwip/inet.h"
 #include "netif/ethernet.h"
 #include "lwip/stats.h"
 #include "lwip/prot/iana.h"

test/unit/tcp/tcp_helper.c

@@ -3,6 +3,7 @@
 #include "lwip/priv/tcp_priv.h"
 #include "lwip/stats.h"
 #include "lwip/pbuf.h"
+#include "lwip/inet.h"
 #include "lwip/inet_chksum.h"
 #include "lwip/ip_addr.h"
 

test/unit/tcp/test_tcp.c

@@ -2,6 +2,7 @@
 
 #include "lwip/priv/tcp_priv.h"
 #include "lwip/stats.h"
+#include "lwip/inet.h"
 #include "tcp_helper.h"
 #include "lwip/inet_chksum.h"