message: Fix variable shadowing wallet/walletdb.cpp
  wallet/walletdb.cpp:930:48: warning: declaration shadows a local variable [-Wshadow]
  map<string, int>::iterator mi = bitdb.mapFileUseCount.find(strFile);
  ^
  wallet/walletdb.cpp:920:44: note: previous declaration is here
  map<string, int>::iterator mi = bitdb.mapFileUseCount.begin();
  ^
diff: @@ -937,8 +937,8 @@ void ThreadFlushWalletDB(const string &strFile)
  if (nRefCount == 0)
  {
  boost::this_thread::interruption_point();
  - map<string, int>::iterator mi = bitdb.mapFileUseCount.find(strFile);
  - if (mi != bitdb.mapFileUseCount.end())
  + map<string, int>::iterator mi2 = bitdb.mapFileUseCount.find(strFile);
  + if (mi2 != bitdb.mapFileUseCount.end())
  {
  LOG(DBASE, "Flushing wallet.dat\n");
  nLastFlushed = nWalletDBUpdated;
  @@ -948,7 +948,7 @@ void ThreadFlushWalletDB(const string &strFile)
  bitdb.CloseDb(strFile);
  bitdb.CheckpointLSN(strFile);
  - bitdb.mapFileUseCount.erase(mi++);
  + bitdb.mapFileUseCount.erase(mi2++);
  LOG(DBASE, "Flushed wallet.dat %dms\n", GetTimeMillis() - nStart);
  }
  }
  