cache: attempt to automatically re-match hashes on invalidate

This code is slow and unoptimized. Will require some more work.

app/render/framehashcache.h

@@ -66,6 +66,9 @@ public:
 
   static QString GetFormatExtension(const PixelFormat::Format& f);
 
+  static QList<rational> GetFrameListFromTimeRange(TimeRangeList range_list, const rational& timebase);
+  QList<rational> GetFrameListFromTimeRange(const TimeRangeList &range) const;
+
 protected:
   virtual void LengthChangedEvent(const rational& old, const rational& newlen) override;