timeline: overhauled pointer tool again

Allows dynamic switching between pointer/roll/slide since occasionally this
behavior is interchangeable. Fixes a lot of transition behavior (but not
all of it).

app/timeline/trackreference.h

@@ -36,6 +36,8 @@ public:
 
   const int& index() const;
 
+  bool operator<(const TrackReference& ref) const;
+
   bool operator==(const TrackReference& ref) const;
 
 private:
@@ -44,6 +46,8 @@ private:
   int index_;
 };
 
+uint qHash(const TrackReference& r, uint seed);
+
 OLIVE_NAMESPACE_EXIT
 
 #endif // TRACKREFERENCE_H