Doc: Remove page about how to start QThreads

Multiple issues:
- Incomplete: It doesn't talk about instantiating a raw QThread
- Redundant: Its contents are already presented in QThread's class ref
- Incorrect: It is legal to create a QThread before a QCoreApplication
- Irrelevant: The bit about QCoreApplication::exec() and the etymology
  of "GUI thread" is unrelated to the topic of starting threads

Also remove snippets that are no longer used

Change-Id: Ice1819845b5b2cf843719edaa7b0f4bbb1e8bd97
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/doc/snippets/threads/threads.cpp

@@ -42,16 +42,6 @@
 #include <QMutex>
 #include <QThreadStorage>
 
-#include "threads.h"
-
-//! [0]
-void MyThread::run()
-//! [0] //! [1]
-{
-//! [1] //! [2]
-}
-//! [2]
-
 #define Counter ReentrantCounter
 
 //! [3]

src/corelib/doc/snippets/threads/threads.h

@@ -1,51 +0,0 @@
-/****************************************************************************
-**
-** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
-** Contact: http://www.qt-project.org/legal
-**
-** This file is part of the documentation of the Qt Toolkit.
-**
-** $QT_BEGIN_LICENSE:BSD$
-** You may use this file under the terms of the BSD license as follows:
-**
-** "Redistribution and use in source and binary forms, with or without
-** modification, are permitted provided that the following conditions are
-** met:
-**   * Redistributions of source code must retain the above copyright
-**     notice, this list of conditions and the following disclaimer.
-**   * Redistributions in binary form must reproduce the above copyright
-**     notice, this list of conditions and the following disclaimer in
-**     the documentation and/or other materials provided with the
-**     distribution.
-**   * Neither the name of Digia Plc and its Subsidiary(-ies) nor the names
-**     of its contributors may be used to endorse or promote products derived
-**     from this software without specific prior written permission.
-**
-**
-** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
-**
-** $QT_END_LICENSE$
-**
-****************************************************************************/
-
-#include <QThread>
-
-//! [0]
-class MyThread : public QThread
-{
-    Q_OBJECT
-
-protected:
-    void run();
-};
-//! [0]

src/corelib/doc/src/threads.qdoc

@@ -60,7 +60,6 @@
     \li \l{Recommended Reading}
     \li \l{The Threading Classes}
     \li \l{Multithreading Technologies in Qt}
-    \li \l{Starting Threads with QThread}
     \li \l{Synchronizing Threads}
     \li \l{Reentrancy and Thread-Safety}
     \li \l{Threads and QObjects}
@@ -122,7 +121,7 @@
 
     \contentspage Thread Support in Qt
     \previouspage Thread Support in Qt
-    \nextpage Starting Threads with QThread
+    \nextpage Synchronizing Threads
 
     Qt offers many classes and functions for working with threads. Below are
     three different approaches that Qt programmers can use to implement
@@ -284,61 +283,11 @@
     \endtable
 */
 
-/*!
-    \page threads-starting.html
-    \title Starting Threads with QThread
-
-    \contentspage Thread Support in Qt
-    \previouspage Multithreading Technologies in Qt
-    \nextpage Synchronizing Threads
-
-    A QThread instance represents a thread and provides the means to
-    \l{QThread::start()}{start()} a thread, which will then execute the
-    reimplementation of QThread::run(). The \c run() implementation is for a
-    thread what the \c main() entry point is for the application. All code
-    executed in a call stack that starts in the \c run() function is executed
-    by the new thread, and the thread finishes when the function returns.
-    QThread emits signals to indicate that the thread started or finished
-    executing.
-
-    \section1 Creating a Thread
-
-    To create a thread, subclass QThread and reimplement its
-    \l{QThread::run()}{run()} function. For example:
-
-    \snippet threads/threads.h 0
-    \codeline
-    \snippet threads/threads.cpp 0
-    \snippet threads/threads.cpp 1
-    \dots
-    \snippet threads/threads.cpp 2
-
-    \section1 Starting a Thread
-
-    Then, create an instance of the thread object and call
-    QThread::start(). Note that you must create the QApplication (or
-    QCoreApplication) object before you can create a QThread.
-
-    The function will return immediately and the
-    main thread will continue. The code that appears in the
-    \l{QThread::run()}{run()} reimplementation will then be executed
-    in a separate thread.
-
-    Creating threads is explained in more detail in the QThread
-    documentation.
-
-    Note that QCoreApplication::exec() must always be called from the
-    main thread (the thread that executes \c{main()}), not from a
-    QThread. In GUI applications, the main thread is also called the
-    GUI thread because it's the only thread that is allowed to
-    perform GUI-related operations.
-*/
-
 /*!
     \page threads-synchronizing.html
     \title Synchronizing Threads
 
-    \previouspage Starting Threads with QThread
+    \previouspage Multithreading Technologies in Qt
     \contentspage Thread Support in Qt
     \nextpage Reentrancy and Thread-Safety