Make test_bitcoin.cpp compatible with Qt Test framework

Move Boost.Test main function and global overrides to a new test_bitcoin_main.cpp file.

src/test/test_bitcoin_main.cpp

@@ -0,0 +1,26 @@
+// Copyright (c) 2011-2016 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#define BOOST_TEST_MODULE Bitcoin Test Suite
+
+#include "net.h"
+
+#include <boost/test/unit_test.hpp>
+
+std::unique_ptr<CConnman> g_connman;
+
+void Shutdown(void* parg)
+{
+  exit(EXIT_SUCCESS);
+}
+
+void StartShutdown()
+{
+  exit(EXIT_SUCCESS);
+}
+
+bool ShutdownRequested()
+{
+  return false;
+}