Minimal changes to comply with explicit CMutableTransaction -> CTranaction conversion.

This commit makes the minimal changes necessary to fix compilation once CTransaction(const CMutableTransaction &tx) is made explicit. In each case an explicit call `CTransaction(...)` was added. Shouldn't affect behaviour or performance.

src/bitcoin-tx.cpp

@@ -818,7 +818,7 @@ static int CommandLineRawTx(int argc, char* argv[])
             MutateTx(tx, key, value);
         }
 
-        OutputTx(tx);
+        OutputTx(CTransaction(tx));
     }
     catch (const std::exception& e) {
         strPrint = std::string("error: ") + e.what();