qdnslookup tool: add the ability to resolve hostnames

We always just take the first, which QHostInfo should have sorted in
priority order.

Change-Id: I455fe22ef4ad4b2f9b01fffd17c7bc6460f06b98
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

tests/manual/qdnslookup/main.cpp

@@ -54,6 +54,13 @@ static auto parseServerAddress(QString server)
 
     r.port = url.port();
     r.address.setAddress(url.host());
+    if (r.address.isNull()) {
+        // try to resolve a hostname
+        QHostInfo hostinfo = QHostInfo::fromName(url.host());
+        const QList<QHostAddress> addresses = hostinfo.addresses();
+        if (!hostinfo.error() && !addresses.isEmpty())
+            r.address = addresses.at(0);
+    }
     return r;
 }