Specify non-standard transaction error when it's dust

Signed-off-by: Anthony Fieroni <bvbfan@abv.bg>

src/main.cpp

@@ -1034,8 +1034,12 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
 
     // Rather not work on nonstandard transactions (unless -testnet/-regtest)
     string reason;
-    if (fRequireStandard && !IsStandardTx(tx, reason))
-        return state.DoS(0, false, REJECT_NONSTANDARD, reason);
+    if (fRequireStandard && !IsStandardTx(tx, reason)) {
+        if (reason == "dust")
+            return state.DoS(0, false, REJECT_DUST, reason);
+        else
+            return state.DoS(0, false, REJECT_NONSTANDARD, reason);
+    }
 
     // Don't relay version 2 transactions until CSV is active, and we can be
     // sure that such transactions will be mined (unless we're on