Backport make_unique

C++14 has std::make_unique, which is convenient for working with unique_ptrs.

It is sufficient to backport only the overload for non-array types, the
overload for array types isn't used in ndn-cxx.

Change-Id: I200ba24ace6ed25d695f0ebe5e9b459f5dfc7538
Refs: #3093
diff --git a/src/security/key-chain.hpp b/src/security/key-chain.hpp
index c9ed28c..c5082d3 100644
--- a/src/security/key-chain.hpp
+++ b/src/security/key-chain.hpp
@@ -911,7 +911,7 @@
 KeyChain::registerPib(std::initializer_list<std::string> aliases)
 {
   registerPibImpl(*aliases.begin(), aliases, [] (const std::string& locator) {
-      return unique_ptr<SecPublicInfo>(new PibType(locator));
+      return make_unique<PibType>(locator);
     });
 }
 
@@ -920,7 +920,7 @@
 KeyChain::registerTpm(std::initializer_list<std::string> aliases)
 {
   registerTpmImpl(*aliases.begin(), aliases, [] (const std::string& locator) {
-      return unique_ptr<SecTpm>(new TpmType(locator));
+      return make_unique<TpmType>(locator);
     });
 }