message: Add checkpoint status to getinfo
diff: #include "walletdb.h"
  #include "init.h"
  #include "base58.h"
  +#include "checkpointsync.h"
  #include <boost/assign/list_of.hpp>
  @@ -95,6 +96,7 @@ Value getinfo(const Array& params, bool fHelp)
  obj.push_back(Pair("keypoololdest", (boost::int64_t)pwalletMain->GetOldestKeyPoolTime()));
  obj.push_back(Pair("keypoolsize", pwalletMain->GetKeyPoolSize()));
  obj.push_back(Pair("paytxfee", ValueFromAmount(nTransactionFee)));
  + obj.push_back(Pair("checkpoints", IsSyncCheckpointEnforced()));
  if (pwalletMain->IsCrypted())
  obj.push_back(Pair("unlocked_until", (boost::int64_t)nWalletUnlockTime));
  obj.push_back(Pair("errors", GetWarnings("statusbar")));
  