message: wallet: refactor: inline function WriteOrderPos()
  Since accounts were removed in commit
  this function is only called at one place and thus can be as well inlined.
diff: typedef std::map<std::string, std::string> mapValue_t;
  -
  -static inline void WriteOrderPos(const int64_t& nOrderPos, mapValue_t& mapValue)
  -{
  - if (nOrderPos == -1)
  - return;
  - mapValue["n"] = ToString(nOrderPos);
  -}
  -
  /** Legacy class used for deserializing vtxPrev for backwards compatibility.
  * vtxPrev was removed in commit 93a18a3650292afbb441a47d1fa1b94aeb0164e3,
  * but old wallet.dat files may still contain vtxPrev vectors of CMerkleTxs.
  @@ -181,7 +173,9 @@ public:
  mapValue_t mapValueCopy = mapValue;
  mapValueCopy["fromaccount"] = "";
  - WriteOrderPos(nOrderPos, mapValueCopy);
  + if (nOrderPos != -1) {
  + mapValueCopy["n"] = ToString(nOrderPos);
  + }
  if (nTimeSmart) {
  mapValueCopy["timesmart"] = strprintf("%u", nTimeSmart);
  }
  