message: Change polltimer1 trigger from 250ms to 500ms
  This provides ample responsiveness in the UI while
  at the same time reducing the number of locks taken
  on mempool.cs by a factor of 2 times.
diff: #define BITCOIN_QT_GUICONSTANTS_H
  /* Milliseconds between model updates */
  -static const int MODEL_UPDATE_DELAY1 = 250;
  +static const int MODEL_UPDATE_DELAY1 = 500;
  static const int MODEL_UPDATE_DELAY2 = 5000;
  /* AskPassphraseDialog -- Maximum passphrase length */
  