message: Fix printf warning in the cpu miner
  ../../src/bitcoin-miner.cpp:341:80: warning: format specifies type 'long' but the argument has type 'long long' [-Wformat]
  printf("Checked %d possibilities in %ld secs, %3.3f MH/s\n", nChecked, elapsed / 1000,
  ~~~                                ^~~~~~~~~~~~~~
  %lld
diff: @@ -338,7 +338,7 @@ static UniValue CpuMineBlock(unsigned int searchDuration, const UniValue &params
  if (!found)
  {
  const auto elapsed = GetTimeMillis() - start;
  - printf("Checked %d possibilities in %ld secs, %3.3f MH/s\n", nChecked, elapsed / 1000,
  + printf("Checked %d possibilities in %lld secs, %3.3f MH/s\n", nChecked, elapsed / 1000,
  (nChecked / 1e6) / (elapsed / 1e3));
  return ret;
  }
  