Auto merge of #1126 - ebfull:more-libsnark-changes, r=ebfull

Remove more from libsnark, and fix potential remote-DoS.

See https://github.com/zcash/libsnark/pull/1 as well.

[`59adbef`](59adbefcc8) removes a remote-DoS that can occur if proofs are not well-formed.

[`e3779f9`](e3779f9049) removes more files that we do not need from libsnark.

[`11242d8`](11242d8afe) replaces assertions that could be triggered by our verifier with exceptions.

Here in Zcash, we catch all exceptions from the verifier and return false.

Closes #459, Closes #69

src/zcash/JoinSplit.cpp

@@ -157,7 +157,11 @@ public:
             vpub_new
         );
 
-        return r1cs_ppzksnark_verifier_strong_IC<ppzksnark_ppT>(*vk, witness, r1cs_proof);
+        try {
+            return r1cs_ppzksnark_verifier_strong_IC<ppzksnark_ppT>(*vk, witness, r1cs_proof);
+        } catch (...) {
+            return false;
+        }
     }
 
     boost::array<unsigned char, ZKSNARK_PROOF_SIZE> prove(