Fixed build bug on Ubuntu

Some quick googling led me to this similar fix: 
https://github.com/rat4/blackcoin/pull/15/files

src/net.cpp

@@ -57,7 +57,7 @@ static bool vfLimited[NET_MAX] = {};
 static CNode* pnodeLocalHost = NULL;
 CAddress addrSeenByPeer(CService("0.0.0.0", 0), nLocalServices);
 uint64 nLocalHostNonce = 0;
-array<int, THREAD_MAX> vnThreadsRunning;
+boost::array<int, THREAD_MAX> vnThreadsRunning;
 static std::vector<SOCKET> vhListenSocket;
 CAddrMan addrman;