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/script/scriptengine.cpp

@@ -46,6 +46,7 @@
 #include "stackhandler.h"
 #include "watchhandler.h"
 #include "watchutils.h"
+#include "debuggertooltipmanager.h"
 
 #include <utils/qtcassert.h>
 
@@ -512,11 +513,10 @@ static QPoint m_toolTipPos;
 static QHash<QString, WatchData> m_toolTipCache;
 
 void ScriptEngine::setToolTipExpression(const QPoint &mousePos,
-    TextEditor::ITextEditor *editor, int cursorPos)
+    TextEditor::ITextEditor *editor, const DebuggerToolTipContext &ctx)
 {
     Q_UNUSED(mousePos)
     Q_UNUSED(editor)
-    Q_UNUSED(cursorPos)
 
     if (state() != InferiorStopOk) {
         //SDEBUG("SUPPRESSING DEBUGGER TOOLTIP, INFERIOR NOT STOPPED");
@@ -530,7 +530,7 @@ void ScriptEngine::setToolTipExpression(const QPoint &mousePos,
 
     int line;
     int column;
-    QString exp = cppExpressionAt(editor, cursorPos, &line, &column);
+    QString exp = cppExpressionAt(editor, ctx.position, &line, &column);
 
 /*
     if (m_toolTipCache.contains(exp)) {