Remove shutdown parameter from close call

Pros
- Simplifies interface
- Easier base implementation

Cons
- May need shutdown functionality, in this case shutdown
  can be added as another function in the future

NetworkInterface.h

@@ -201,9 +201,8 @@ protected:
 
     /** Close the socket
      *  @param handle   Socket handle
-     *  @param shutdown free the left-over data in message queues
      */
-    virtual int socket_close(void *handle, bool shutdown) = 0;
+    virtual int socket_close(void *handle) = 0;
 
     /** Register a callback on when a new connection is ready
      *  @param handle   Socket handle

Socket.cpp

@@ -27,7 +27,7 @@ Socket::Socket()
 Socket::~Socket()
 {
     if (_socket) {
-        close(false);
+        close();
     }
 }
 
@@ -37,13 +37,13 @@ int Socket::open(NetworkInterface *iface, nsapi_protocol_t proto)
     _socket = _iface->socket_create(proto);
 }
 
-int Socket::close(bool shutdown)
+int Socket::close()
 {
     if (!_socket) {
         return 0;
     }
 
-    int err = _iface->socket_close(_socket, shutdown);
+    int err = _iface->socket_close(_socket);
     if (!err) {
         void *socket = _socket;
         _socket = 0;

Socket.h

@@ -60,9 +60,8 @@ public:
     int get_option(int optname, void *optval, unsigned *optlen);
     
     /** Close the socket
-     *  @param shutdown free the left-over data in message queues
      */
-    int close(bool shutdown=true);
+    int close();
 
 protected:
     Socket();