Add SCRIPT_VERIFY_SIGPUSHONLY (BIP62 rule 2)

src/script/interpreter.h

@@ -46,6 +46,9 @@ enum
 
     // verify dummy stack item consumed by CHECKMULTISIG is of zero-length (softfork safe, BIP62 rule 7).
     SCRIPT_VERIFY_NULLDUMMY = (1U << 4),
+
+    // Using a non-push operator in the scriptSig causes script failure (softfork safe, BIP62 rule 2).
+    SCRIPT_VERIFY_SIGPUSHONLY = (1U << 5),
 };
 
 uint256 SignatureHash(const CScript &scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType);