Compile-fix: add missing declaration in debug.

QAbstractSocketPrivate::readFromSocket() had a qDebug() that
references its q->... so it also needs its Q_Q() declaration.
Only relevant when QABSTRACTSOCKET_DEBUG is enabled (which it
normally isn't).

Change-Id: Ib82fd032fb2c4143a0987b9162377d0d7e968e95
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/network/socket/qabstractsocket.cpp

@@ -1248,6 +1248,10 @@ void QAbstractSocketPrivate::_q_forceDisconnect()
 */
 bool QAbstractSocketPrivate::readFromSocket()
 {
+#ifdef QABSTRACTSOCKET_DEBUG
+    Q_Q(QAbstractSocket);
+#endif
+
     // Find how many bytes we can read from the socket layer.
     qint64 bytesToRead = socketEngine->bytesAvailable();
     if (bytesToRead == 0) {