Debugger: Make tooltips pinnable.

Replace old debugger tooltip by a new ToolTipManager which
has a list of AbstractDebuggerToolTipWidget with the functionality
to 'acquire' an engine (display its data) and 'release' it
(store engine data and display them as 'previous') and serialization
to XML session data.
DebuggerTreeViewToolTipWidget implements AbstractDebuggerToolTipWidget
for tree model acting as  a filter on watch models.

Rubber-stamped-by: hjk

src/plugins/debugger/qml/qmlengine.cpp

@@ -42,7 +42,7 @@
 #include "debuggermainwindow.h"
 #include "debuggerrunner.h"
 #include "debuggerstringutils.h"
-#include "debuggertooltip.h"
+#include "debuggertooltipmanager.h"
 
 #include "breakhandler.h"
 #include "moduleshandler.h"
@@ -564,11 +564,11 @@ void QmlEngine::requestModuleSymbols(const QString &moduleName)
 //////////////////////////////////////////////////////////////////////
 
 void QmlEngine::setToolTipExpression(const QPoint &mousePos,
-    TextEditor::ITextEditor *editor, int cursorPos)
+    TextEditor::ITextEditor *editor, const DebuggerToolTipContext &ctx)
 {
     // This is processed by QML inspector, which has dependencies to 
     // the qml js editor. Makes life easier.
-    emit tooltipRequested(mousePos, editor, cursorPos);
+    emit tooltipRequested(mousePos, editor, ctx.position);
 }
 
 //////////////////////////////////////////////////////////////////////