Add namespace TextEditor around DocumentMarker

Missed in moving the class

Change-Id: Iec712b64338d0ec84d7aa599d36f1a7845be2a74
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/texteditor/basetextdocumentlayout.cpp

@@ -35,6 +35,7 @@
 
 using namespace TextEditor;
 
+namespace TextEditor {
 namespace Internal {
 
 class DocumentMarker : public ITextMarkable
@@ -147,6 +148,7 @@ void DocumentMarker::updateMark(ITextMark *mark)
 }
 
 } // namespace Internal
+} // namespace TextEditor
 
 CodeFormatterData::~CodeFormatterData()
 {