fix shutdown paths

this includes:
- move the gdb ownership back to the engine (thus strip down the
  adaptors as far as possible)
- make gdb startup synchronous
- make adapter shutdown synchronous
- fix the state transitions relating to shutdown

src/plugins/debugger/gdb/abstractgdbadapter.cpp

@@ -47,35 +47,18 @@ AbstractGdbAdapter::~AbstractGdbAdapter()
     disconnect();
 }
 
-// This cannot be in the c'tor, as it would not connect the "virtual" slots
-void AbstractGdbAdapter::commonInit()
+void AbstractGdbAdapter::shutdown()
 {
-    QTC_ASSERT(state() == EngineStarting, qDebug() << state());
-    connect(&m_gdbProc, SIGNAL(error(QProcess::ProcessError)),
-        this, SLOT(handleGdbError(QProcess::ProcessError)));
-    connect(&m_gdbProc, SIGNAL(started()),
-        this, SLOT(handleGdbStarted()));
-    connect(&m_gdbProc, SIGNAL(finished(int, QProcess::ExitStatus)),
-        this, SLOT(handleGdbFinished(int, QProcess::ExitStatus)));
-    connect(&m_gdbProc, SIGNAL(readyReadStandardOutput()),
-        this, SIGNAL(readyReadStandardOutput()));
-    connect(&m_gdbProc, SIGNAL(readyReadStandardError()),
-        this, SIGNAL(readyReadStandardError()));
 }
 
-QByteArray AbstractGdbAdapter::readAllStandardOutput()
+const char *AbstractGdbAdapter::inferiorShutdownCommand() const
 {
-    return m_gdbProc.readAllStandardOutput();
-}
-
-QByteArray AbstractGdbAdapter::readAllStandardError()
-{
-    return m_gdbProc.readAllStandardError();
+    return "kill";
 }
 
 void AbstractGdbAdapter::write(const QByteArray &data)
 {
-    m_gdbProc.write(data);
+    m_engine->m_gdbProc.write(data);
 }
 
 bool AbstractGdbAdapter::isTrkAdapter() const