Use singleton block tree database instance

src/init.cpp

@@ -79,8 +79,10 @@ void Shutdown(void* parg)
         {
             LOCK(cs_main);
             pcoinsTip->Flush();
+            pblocktree->Flush();
             delete pcoinsTip;
             delete pcoinsdbview;
+            delete pblocktree;
         }
         bitdb.Flush(true);
         boost::filesystem::remove(GetPidFile());
@@ -650,6 +652,7 @@ bool AppInit2()
     uiInterface.InitMessage(_("Loading block index..."));
     printf("Loading block index...\n");
     nStart = GetTimeMillis();
+    pblocktree = new CBlockTreeDB("cr+");
     pcoinsdbview = new CCoinsViewDB();
     pcoinsTip = new CCoinsViewCache(*pcoinsdbview);