Add support for annotation of any given revision

- Parent commits are also accessible from Annotate context menu
- The client functionality was added in `fossil v2.4`

Change-Id: Ia6096432cb1151388b5aebca30a6d25c1c6079f4
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

plugins/fossil/fossileditor.h

@@ -43,7 +43,10 @@ public:
 private:
     QSet<QString> annotationChanges() const final;
     QString changeUnderCursor(const QTextCursor &cursor) const final;
-    VcsBase::BaseAnnotationHighlighter *createAnnotationHighlighter(const QSet<QString> &changes) const final;
+    QString decorateVersion(const QString &revision) const final;
+    QStringList annotationPreviousVersions(const QString &revision) const final;
+    VcsBase::BaseAnnotationHighlighter *createAnnotationHighlighter(
+            const QSet<QString> &changes) const final;
 
     FossilEditorWidgetPrivate *d;
 };