Add simple test for ptr::make_unique

src/Unittests/unittests_smartptr.cc

+#include <gtest/gtest.h>
+
+#include <OpenVolumeMesh/System/MemoryInclude.hh>
+
+TEST(MakeUniqueTest, MakeUniqueTest) {
+  std::unique_ptr<int> foo;
+  auto bar = ptr::make_unique<int>(5);
+  foo = std::move(bar);
+
+  EXPECT_EQ(*foo, 5);
+  EXPECT_EQ(bar.get(), nullptr);
+}
+