do not export struct timeval to external users of socket.h to avoid conflicts

src/api/sockets.c

@@ -37,6 +37,7 @@
 #include "lwip/arch.h"
 #include "lwip/sys.h"
 
+#define LWIP_TIMEVAL_PRIVATE
 #include "lwip/sockets.h"
 
 #define NUM_SOCKETS MEMP_NUM_NETCONN

src/include/lwip/sockets.h

@@ -205,10 +205,16 @@ struct linger {
           unsigned char fd_bits [(FD_SETSIZE+7)/8];
         } fd_set;
 
+/* 
+ * only define this in sockets.c so it does not interfere
+ * with other projects namespaces where timeval is present
+ */ 
+#ifdef LWIP_TIMEVAL_PRIVATE
   struct timeval {
     long    tv_sec;         /* seconds */
     long    tv_usec;        /* and microseconds */
   };
+#endif
 
 #endif