Merge remote-tracking branch 'origin/5.9.0' into 5.9

Change-Id: Ic9a7d0f871c1533705f5567a665607403cb983ee

dist/changes-5.9.0

+Qt 5.9 introduces many new features and improvements as well as bugfixes
+over the 5.8.x series. For more details, refer to the online documentation
+included in this distribution. The documentation is also available online:
+
+http://doc.qt.io/qt-5/index.html
+
+The Qt version 5.9 series is binary compatible with the 5.8.x series.
+Applications compiled for 5.8 will continue to run with 5.9.
+
+Some of the changes listed in this file include issue tracking numbers
+corresponding to tasks in the Qt Bug Tracker:
+
+https://bugreports.qt.io/
+
+Each of these identifiers can be entered in the bug tracker to obtain more
+information about a particular change.
+
+****************************************************************************
+*                               Library                                    *
+****************************************************************************
+
+- QWebSocketServer
+ * [QTBUG-56129] SslMode::NonSecure enumerator now always has the same
+   value (1) regardless of SSL being enabled or disabled.
+ * [QTBUG-54276] Added a member function to handle external QTcpSocket,
+   upgrading it to a QWebSocket.
+ * [QTBUG-56414] Server now deletes a websocket when a 'disconnected'
+   signal is received.
+- QWebSocketHandshakeRequest
+   [QTBUG-57357] Fixed the parsing of port in handshake requests.
+- QWebSocketDataProcessor
+   [QTBUG-55506] Call clear() before emitting textMessageReceived or
+   binaryMessageReceived to avoid data corruption in case a slot blocks
+   (for example, entering a nested modal loop while showing this message)
+   while socket receives more data.
+- QQmlWebSocket
+ * [QTBUG-58278] Fix setUrl: only call open() if the 'active' property is
+   true.
+