consensus: guard against openssl's new strict DER checks
consensus: guard against openssl's new strict DER checks

New versions of OpenSSL will reject non-canonical DER signatures. However,
it'll happily decode them. Decode then re-encode before verification in order
to ensure that it is properly consumed.
GroestlCoin/GroestlCoin-obsolete,GroestlCoin/GroestlCoin-obsolete,GroestlCoin/GroestlCoin-obsolete,GroestlCoin/GroestlCoin-obsolete,GroestlCoin/GroestlCoin-obsolete