build: require gcc >= 5.3 and switch to C++14

Change-Id: I93c8fc238cc2654346bbc69a9d8ea83d1c0b099e
Refs: #3076, #4462
diff --git a/src/communication/sync-logic-handler.cpp b/src/communication/sync-logic-handler.cpp
index 7703505..308a15d 100644
--- a/src/communication/sync-logic-handler.cpp
+++ b/src/communication/sync-logic-handler.cpp
@@ -45,7 +45,7 @@
 
 SyncLogicHandler::SyncLogicHandler(ndn::Face& face, const IsLsaNew& isLsaNew,
                                    const ConfParameter& conf)
-  : onNewLsa(ndn::make_unique<OnNewLsa>())
+  : onNewLsa(std::make_unique<OnNewLsa>())
   , m_syncFace(face)
   , m_isLsaNew(isLsaNew)
   , m_confParam(conf)
diff --git a/src/nlsr.cpp b/src/nlsr.cpp
index 3c3fab3..58d4441 100644
--- a/src/nlsr.cpp
+++ b/src/nlsr.cpp
@@ -62,7 +62,7 @@
                      m_nlsrFace,
                      m_keyChain)
   , m_helloProtocol(*this, scheduler)
-  , m_validator(ndn::make_unique<ndn::security::v2::CertificateFetcherDirectFetch>(m_nlsrFace))
+  , m_validator(std::make_unique<ndn::security::v2::CertificateFetcherDirectFetch>(m_nlsrFace))
   , m_controller(m_nlsrFace, m_keyChain)
   , m_faceDatasetController(m_nlsrFace, m_keyChain)
   , m_prefixUpdateProcessor(m_dispatcher,
diff --git a/src/route/routing-table.cpp b/src/route/routing-table.cpp
index 1f88c87..9c4ea77 100644
--- a/src/route/routing-table.cpp
+++ b/src/route/routing-table.cpp
@@ -17,6 +17,7 @@
  * You should have received a copy of the GNU General Public License along with
  * NLSR, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
  **/
+
 #include "routing-table.hpp"
 #include "nlsr.hpp"
 #include "map.hpp"
@@ -35,7 +36,7 @@
 INIT_LOGGER(route.RoutingTable);
 
 RoutingTable::RoutingTable(ndn::Scheduler& scheduler)
-  : afterRoutingChange{ndn::make_unique<AfterRoutingChange>()}
+  : afterRoutingChange{std::make_unique<AfterRoutingChange>()}
   , m_scheduler(scheduler)
   , m_NO_NEXT_HOP{-12345}
   , m_routingCalcInterval{static_cast<uint32_t>(ROUTING_CALC_INTERVAL_DEFAULT)}
diff --git a/src/update/prefix-update-processor.cpp b/src/update/prefix-update-processor.cpp
index 26adefd..57bb579 100644
--- a/src/update/prefix-update-processor.cpp
+++ b/src/update/prefix-update-processor.cpp
@@ -54,8 +54,7 @@
                                              NamePrefixList& namePrefixList,
                                              Lsdb& lsdb)
   : CommandManagerBase(dispatcher, namePrefixList, lsdb, "prefix-update")
-
-  , m_validator(ndn::make_unique<ndn::security::v2::CertificateFetcherDirectFetch>(face))
+  , m_validator(std::make_unique<ndn::security::v2::CertificateFetcherDirectFetch>(face))
 {
   NLSR_LOG_DEBUG("Setting dispatcher to capture Interests for: "
     << ndn::Name(Nlsr::LOCALHOST_PREFIX).append("prefix-update"));