Auto merge of #1311 - ebfull:cleanup-pp, r=ebfull

Deallocate the public parameters during Shutdown.

This also has it deallocated in `GenerateParams` and `test_bitcoin`. The virtual destructor probably isn't necessary but I added it just in case we need it some other time.

src/zcash/JoinSplit.cpp

@@ -72,6 +72,9 @@ public:
     boost::optional<r1cs_ppzksnark_verification_key<ppzksnark_ppT>> vk;
     boost::optional<std::string> pkPath;
 
+    JoinSplitCircuit() {}
+    ~JoinSplitCircuit() {}
+
     static void initialize() {
         LOCK(cs_InitializeParams);
 
@@ -122,8 +125,6 @@ public:
         vk = keypair.vk;
     }
 
-    JoinSplitCircuit() {}
-
     bool verify(
         const ZCProof& proof,
         const uint256& pubKeyHash,