Fix QDnslookup build on FreeBSD

Unify the includes for resolver function on unix-like platforms
to avoid build failures on BSD platforms.

Change-Id: I9accd7077d5a319a2c93642e011492d0fc779394
Reviewed-by: Holger Freyther <holger+qt@freyther.de>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/network/kernel/qdnslookup_unix.cpp

@@ -47,11 +47,9 @@
 #include <private/qmutexpool_p.h>
 
 #include <sys/types.h>
-#include <netdb.h>
-#if defined(Q_OS_MAC)
+#include <netinet/in.h>
 #include <arpa/nameser.h>
 #include <arpa/nameser_compat.h>
-#endif
 #include <resolv.h>
 
 QT_BEGIN_NAMESPACE