libevent seems to have invaded `libbitcoin_common` via `url.cpp`

`url.cpp` is used only from `test/fuzz/string.cpp` and `wallet/rpcwallet.cpp`

libevent should only be required for bitcoind, bitcoin-cli and (due only to the hack of passing wallet names) bitcoin-qt

NO_STDIN_ECHO();
            if (!StdinReady()) {
                fputs("RPC password> ", stderr);
                fflush(stderr);
            }
            if (!std::getline(std::cin, rpcPass)) {
                throw std::runtime_error("-stdinrpcpass specified but failed to read from standard input");
            }
            if (StdinTerminal()) {
                fputc('\n', stdout);
            }
            gArgs.ForceSetArg("-rpcpassword", rpcPass);
        }
        std::vector<std::string> args = std::vector<std::string>(&argv[1], &argv[argc]);
        if (gArgs.GetBoolArg("-stdinwalletpassphrase", false)) {
            NO_STDIN_ECHO();
            std::string walletPass;
            if (args.size() < 1 || args[0].substr(0, 16) != "walletpassphrase") {
                throw std::runtime_error("-stdinwalletpassphrase is only applicable for walletpassphrase(change)");
            }
            if (!StdinReady()) {
                fputs("Wallet passphrase> ", stderr);
                fflush(stderr);
            }
            if (!std::getline(std::cin, walletPass)) {
                throw std::runtime_error("-stdinwalletpassphrase specified but failed to read from standard input");
            }
            if (StdinTerminal()) {
                fputc('\n', stdout);
            }