Merge pull request #332 from fireice-uk/pragma-once

Fix missing pragma once

src/CryptoNoteCore/BlockIndex.h

@@ -5,6 +5,8 @@
 // Distributed under the MIT/X11 software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#pragma once
+
 #include <boost/multi_index_container.hpp>
 #include <boost/multi_index/hashed_index.hpp>
 #include <boost/multi_index/random_access_index.hpp>