message: Add dev doc to CCoinsStats::m_hash_type and make it const
diff: @@ -24,9 +24,10 @@ enum class CoinStatsHashType {
  NONE,
  };
  -struct CCoinsStats
  -{
  - CoinStatsHashType m_hash_type;
  +struct CCoinsStats {
  + //! Which hash type to use
  + const CoinStatsHashType m_hash_type;
  +
  int nHeight{0};
  uint256 hashBlock{};
  uint64_t nTransactions{0};
  