libsecp256k1 now has a pkg-config file so rely on that for autodetecting the pkg.
libsecp256k1 now has a pkg-config file so rely on that for autodetecting the pkg.

libmetrocoin/libmetrocoin-consensus,libtetcoin/libtetcoin-consensus,GroestlCoin/libgroestlcoin,libmetrocoin/libmetrocoin-consensus,swansontec/libbitcoin,libmetrocoin/libmetrocoin-consensus,swansontec/libbitcoin,swansontec/libbitcoin,libtetcoin/libtetcoin-consensus,GroestlCoin/libgroestlcoin,libtetcoin/libtetcoin-consensus,GroestlCoin/libgroestlcoin,libmetrocoin/libmetrocoin-consensus,libmetrocoin/libmetrocoin-consensus,libtetcoin/libtetcoin-consensus,GroestlCoin/libgroestlcoin,libtetcoin/libtetcoin-consensus,swansontec/libbitcoin