CKey: add method to negate the key

src/key.h

@@ -98,6 +98,9 @@ public:
     //! Generate a new private key using a cryptographic PRNG.
     void MakeNewKey(bool fCompressed);
 
+    //! Negate private key
+    bool Negate();
+
     /**
      * Convert the private key to a CPrivKey (serialized OpenSSL private key data).
      * This is expensive.