query_classifier.cc

resolve_query_type, added GSYSVAR_FUNC type for functions that read system variables and can be executed in Maxscale instead of backend server.

dcb.c
	dcb_read, if read returns value <= 0 and if error is EAGAIN/EWOULDBLOCK so there was nothing to read in sthe socket, that is not an error because some other thread may have read the data that was expected to be available.

mysql_backend.c
	gw_read_backend_event, used dcb->authlock to ensure that dcb's protocol state is read and modified serially. This removes issues with false authentication failures which may happen when two threads modify and read the state without any control.

mysql_client.c 
	removed dead code.

readconnroute.c, readwritesplit.c
	removed invalid assert which assumed that spinlock can not have larger value than one when itis locked.

server/modules/protocol/mysql_client.c

@@ -983,13 +983,6 @@ int gw_MySQLAccept(DCB *listener)
                         c_sock);
                 conn_open[c_sock] = true;
 #endif
-                /*
-                fprintf(stderr,
-                        "Processing %i connection fd %i for listener %i\n",
-                        listener->stats.n_accepts,
-                        c_sock,
-                        listener->fd);
-                */
                 /* set nonblocking  */
                 setsockopt(c_sock, SOL_SOCKET, SO_SNDBUF, &sendbuf, optlen);
                 setnonblocking(c_sock);