message: Made expicit constructor CTransaction(const CMutableTransaction &tx).
  This makes the above constructor explicit. The rationale is that this conversion has very significant performance effects. Making it explicit makes it easier to reason about these performance trade-offs, and helps identify possible functions that need a CMutableTransaction version.
diff: @@ -298,7 +298,7 @@ public:
  CTransaction();
  /** Convert a CMutableTransaction into a CTransaction. */
  - CTransaction(const CMutableTransaction &tx);
  + explicit CTransaction(const CMutableTransaction &tx);
  CTransaction(CMutableTransaction &&tx);
  template <typename Stream>
  