VCS editors: Fix revision markers

Resets the revisions when setting the contents of text editor documents
in general.

Task-number: QTCREATORBUG-11356
Change-Id: I4069d629d8a612d42c7deae707300d50690e2db7
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/texteditor/basetextdocument.h

@@ -105,6 +105,7 @@ public:
     virtual bool open(QString *errorString, const QString &fileName, const QString &realFileName);
     virtual bool reload(QString *errorString);
 
+    bool setPlainText(const QString &text);
     QTextDocument *document() const;
     void setSyntaxHighlighter(SyntaxHighlighter *highlighter);
     SyntaxHighlighter *syntaxHighlighter() const;