vcmi: specialize native terrain entity

Specialize native terrain entity for all object that have
native terrain. Allow creatures to take global bonuses into
account when checking for native terrain.

lib/BasicTypes.cpp

@@ -0,0 +1,20 @@
+/*
+ * BasicTypes.cpp, part of VCMI engine
+ *
+ * Authors: listed in file AUTHORS in main folder
+ *
+ * License: GNU General Public License v2.0 or later
+ * Full text of license available in license.txt file, in main folder
+ *
+ */
+
+#include "StdInc.h"
+#include "GameConstants.h"
+
+#include <vcmi/Entity.h>
+
+bool INativeTerrainProvider::isItNativeTerrain(TerrainId terrain) const
+{
+	auto native = getNativeTerrain();
+	return native == terrain || native == ETerrainId::ANY_TERRAIN;
+}