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

{
        return reply.get_obj();
    }
};
static UniValue CallRPC(BaseRequestHandler *rh, const std::string& strMethod, const std::vector<std::string>& args)
{
    std::string host;
    
    
    
    
    int port = BaseParams().RPCPort();
    SplitHostPort(gArgs.GetArg("-rpcconnect", DEFAULT_RPCCONNECT), port, host);
    port = gArgs.GetArg("-rpcport", port);
    
    raii_event_base base = obtain_event_base();
    
    raii_evhttp_connection evcon = obtain_evhttp_connection_base(base.get(), host, port);
    
    {
        const int timeout = gArgs.GetArg("-rpcclienttimeout", DEFAULT_HTTP_CLIENT_TIMEOUT);
        if (timeout > 0) {
            evhttp_connection_set_timeout(evcon.get(), timeout);
        } else {