message: BitFlagIterator: add constructor to start from a specified bit
diff: @@ -32,6 +32,7 @@ private:
  public:
  inline BitFlagIterator() : flags(0) {}
  inline BitFlagIterator(FlagType mask) : flags(mask) {}
  + inline BitFlagIterator(FlagType mask, BitType bit) : flags(mask & ~(bit - 1)) {}
  inline BitFlagIterator(const BitFlagIterator &o) : flags(o.flags) {}
  static inline BitFlagIterator begin(FlagType mask) { return BitFlagIterator(mask); }
  static inline BitFlagIterator end() { return BitFlagIterator(0); }
  