Optimize BaseTextMark

Instead of each BaseTextMark being a QObject and being connected
to editorOpened, centralize that and distribute the signal
to only the BaseTextMarks that need it.

Change-Id: I3f2783c34a25d78aa335418236850436028bfdf3
Reviewed-by: Eike Ziller <eike.ziller@nokia.com>

src/plugins/texteditor/itexteditor.cpp

@@ -38,6 +38,11 @@
 
 using namespace TextEditor;
 
+ITextMark::~ITextMark()
+{
+
+}
+
 void ITextMark::paint(QPainter *painter, const QRect &rect) const
 {
     m_icon.paint(painter, rect, Qt::AlignCenter);