Problem: asserts if EINVAL recieved on read/write

This causes assertion failures after network reconnects.

Solution: allow EINVAL as a possible condition after read/write.

Fixes #829
Fixes #1399

Patch provided by Michele Dionisio @mdionisio, thanks :)

src/tcp.cpp

@@ -218,7 +218,6 @@ void zmq::tune_tcp_retransmit_timeout (fd_t sockfd_, int timeout_)
                    && errno != EBADF
                    && errno != EDESTADDRREQ
                    && errno != EFAULT
-                   && errno != EINVAL
                    && errno != EISCONN
                    && errno != EMSGSIZE
                    && errno != ENOMEM
@@ -269,7 +268,6 @@ int zmq::tcp_read (fd_t s_, void *data_, size_t size_)
     if (rc == -1) {
         errno_assert (errno != EBADF
                    && errno != EFAULT
-                   && errno != EINVAL
                    && errno != ENOMEM
                    && errno != ENOTSOCK);
         if (errno == EWOULDBLOCK || errno == EINTR)