Use src/lib/w32/w32sockets.c for client

Move client's w32_connect() to w32sockets.c.

Replace w32_recv() and w32_send() by read() and write().

Replace w32_close() by w32_close_function.

Replace call of WSAStartup() in w32_sysdep_init() by
w32_socket_init().

Remove the identical copies of fd_is_socket(),
w32_set_winsock_errno(), w32_socket().

src/lib/w32/w32sockets.c

@@ -147,6 +147,25 @@ w32_bind(int fd, const struct sockaddr *name, socklen_t namelen)
     SOCKET_FUNCTION(bind(sock, name, namelen));
 }
 
+/*
+ * POSIX compatible connect() replacement
+ */
+#undef connect
+int
+w32_connect(int sockfd, const struct sockaddr *addr, int addrlen)
+{
+    SOCKET sock = W32_FD_TO_SOCKET(sockfd);
+    int result;
+
+    result = connect(sock, addr, addrlen);
+    if (result == SOCKET_ERROR) {
+	/* FIXME map WSAEWOULDBLOCK to EINPROGRESS */
+	w32_set_winsock_errno();
+	return -1;
+    }
+    return result;
+}
+
 /*
  * POSIX equivalent for listen().
  */