Finetuning Timeline;

- Added Ckey for 'center view around current frame'.
- Completed View pulldown menu with remainder of options.
- prevented negative scaled views when start > end frame

source/blender/include/BSE_time.h

@@ -39,8 +39,9 @@ void add_timeline_marker(int frame);
 void remove_timeline_marker(void);
 void rename_timeline_marker(void);
 void select_timeline_markers(void);
-
+void timeline_frame_to_center(void);
 void nextprev_timeline_key(short dir);
+void nextprev_timeline_marker(short dir);
 
 
 #endif