Haiku: Fix compilation of network library

Like on some BSD systems, the member of the ifreq
structure is called ifr_index and not ifr_ifindex
on Haiku OS.

Change-Id: I273de0c703b1c89dbac537c68e52db219d2da50e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/network/kernel/qnetworkinterface_unix.cpp

@@ -231,7 +231,11 @@ static QNetworkInterfacePrivate *findInterface(int socket, QList<QNetworkInterfa
     // Get the interface index
 #  ifdef SIOCGIFINDEX
     if (qt_safe_ioctl(socket, SIOCGIFINDEX, &req) >= 0)
+#    if defined(Q_OS_HAIKU)
+        ifindex = req.ifr_index;
+#    else
         ifindex = req.ifr_ifindex;
+#    endif
 #  else
     ifindex = if_nametoindex(req.ifr_name);
 #  endif