Re-add a function used by the libwallet URI parser
Re-add a function used by the libwallet URI parser

The libwallet URI parser needs to be identify characters as being base58 or not.
To avoid duplication of code, it makes sense to expose this from
libbitcoin's base58 utility file.

libmetrocoin/libmetrocoin-consensus,swansontec/libbitcoin,libtetcoin/libtetcoin-consensus,Airbitz/libbitcoin,GroestlCoin/libgroestlcoin,libmetrocoin/libmetrocoin-consensus,GroestlCoin/libgroestlcoin,GroestlCoin/libgroestlcoin,libtetcoin/libtetcoin-consensus,kaostao/libbitcoin,BWallet/libbitcoin,swansontec/libbitcoin,libmetrocoin/libmetrocoin-consensus,libmetrocoin/libmetrocoin-consensus,Airbitz/libbitcoin,kaostao/libbitcoin,Airbitz/libbitcoin,libtetcoin/libtetcoin-consensus,swansontec/libbitcoin,BWallet/libbitcoin,BWallet/libbitcoin,libmetrocoin/libmetrocoin-consensus,Airbitz/libbitcoin,GroestlCoin/libgroestlcoin,libtetcoin/libtetcoin-consensus,swansontec/libbitcoin,BWallet/libbitcoin,libtetcoin/libtetcoin-consensus,kaostao/libbitcoin,kaostao/libbitcoin