QProcess/Win can cause malformed heap

Consider a short-lived process that produces some output.

Start this process via QProcess and call waitForFinished.

Then the following can happen:

• in QProcessPrivate::waitForFinished WaitForSingleObject returns WAIT_OBJECT_0
• drainOutputPipes is called and returns.
• The QWindowsPipeReader objects are still active, because the pipe has not been closed yet.
• _q_processDied() is called, which calls cleanup(), which calls QWindowsPipeReader::stop()
• QWindowsPipeReader::stop() sets readSequenceStarted to false, but doesn't cancel the I/O operation (should it rather?)
• waitForFinished() returns
• The QProcess object is destroyed with all its children.
• QWindowsPipeReader with readSequenceStarted==false but an active I/O operation is destroyed.
• The OVERLAPPED object and the read buffer in QWindowsPipeReader is destroyed.
• The active I/O operation modifies the (now destroyed) OVERLAPPED object and, potentially, the read buffer. BAM! The heap is a mess.

This issue originates from QTCREATORBUG-13713.
We can only reproduce it on Windows 7.