Improve pseudo-transaction handling (RIPD-1454, RIPD-1455):

Adds additional checks to prevent relaying and retrying pseudo-transactions.

src/ripple/protocol/impl/STTx.cpp

@@ -504,6 +504,11 @@ bool passesLocalChecks (STObject const& st, std::string& reason)
         return false;
     }
 
+    if (isPseudoTx(st))
+    {
+        reason = "Cannot submit pseudo transactions.";
+        return false;
+    }
     return true;
 }
 
@@ -516,4 +521,14 @@ sterilize (STTx const& stx)
     return std::make_shared<STTx const>(std::ref(sit));
 }
 
+bool
+isPseudoTx(STObject const& tx)
+{
+    auto t = tx[~sfTransactionType];
+    if (!t)
+        return false;
+    auto tt = static_cast<TxType>(*t);
+    return tt == ttAMENDMENT || tt == ttFEE;
+}
+
 } // ripple