fixes to code example

code/addr.cpp

@@ -7,10 +7,13 @@ int main()
     bool success = bc::decode_base16(secret,
         "038109007313a5807b2eccc082c8c3fbb988a973cacf1a7df9ce725c31b14776");
     assert(success);
+   
     // Get public key.
-    bc::ec_point public_key = bc::secret_to_public_key(secret);
-    std::cout << "Public key: " << bc::encode_hex(public_key) << std::endl;
-
+    bc::ec_compressed public_key;
+    success = bc::secret_to_public(public_key, secret);
+    assert(success);
+    std::cout << "Public key: " << bc::encode_base16(public_key) << std::endl;
+    
     // Create Bitcoin address.
     // Normally you can use:
     //   bc::payment_address payaddr;