Do not trigger a DoS ban if SCRIPT_VERIFY_NULLDUMMY fails

src/script.h

@@ -49,6 +49,9 @@ enum
 // them to be valid. (but old blocks may not comply with) Currently just P2SH,
 // but in the future other flags may be added, such as a soft-fork to enforce
 // strict DER encoding.
+//
+// Failing one of these tests may trigger a DoS ban - see CheckInputs() for
+// details.
 static const unsigned int MANDATORY_SCRIPT_VERIFY_FLAGS = SCRIPT_VERIFY_P2SH;
 
 // Standard script verification flags that standard transactions will comply
@@ -58,6 +61,9 @@ static const unsigned int STANDARD_SCRIPT_VERIFY_FLAGS = MANDATORY_SCRIPT_VERIFY
                                                          SCRIPT_VERIFY_STRICTENC |
                                                          SCRIPT_VERIFY_NULLDUMMY;
 
+// For convenience, standard but not mandatory verify flags.
+static const unsigned int STANDARD_NOT_MANDATORY_VERIFY_FLAGS = STANDARD_SCRIPT_VERIFY_FLAGS & ~MANDATORY_SCRIPT_VERIFY_FLAGS;
+
 enum txnouttype
 {
     TX_NONSTANDARD,