[master] Mitigate GCC 5.x optmizer issue in asiolink

    Merged in trac4243.

diff --cc src/bin/dhcp4/dhcp4_srv.cc
Simple merge

diff --cc src/bin/dhcp6/dhcp6_srv.cc
Simple merge

diff --cc src/lib/asiolink/tests/tcp_socket_unittest.cc
Simple merge

diff --cc src/lib/dhcpsrv/tests/memfile_lease_mgr_unittest.cc
index 4f282240298cdbfb6e56c9fcf3ad27473ecc7ba9,558764fafd6bb4df21a51011937b47ff7f13aa8a..a01a54457c06fdf4aa4e4eeb6a642e11209c96c5
--- 1/src/lib/dhcpsrv/tests/memfile_lease_mgr_unittest.cc
--- 2/src/lib/dhcpsrv/tests/memfile_lease_mgr_unittest.cc
+++ b/src/lib/dhcpsrv/tests/memfile_lease_mgr_unittest.cc
@@@ -19,11 -18,10 +18,11 @@@
  #include <dhcpsrv/tests/test_utils.h>
  #include <dhcpsrv/tests/generic_lease_mgr_unittest.h>
  #include <util/pid_file.h>
 +#include <util/range_utilities.h>
  #include <util/stopwatch.h>
- #include <gtest/gtest.h>
  
  #include <boost/bind.hpp>
+ #include <gtest/gtest.h>
  
  #include <cstdlib>
  #include <iostream>