2.5

Added WM Jobs manager
- WM can manage threaded jobs for you; just provide a couple
  of components to get it work:
  - customdata, free callback for it
  - timer step, notifier code
  - start callback, update callback
- Once started, each job runs an own timer, and will for
  every time step check necessary updates, or close the
  job when ready. 
- No drawing happens in jobs, that's for notifiers!
- Every job stores an owner pointer, and based on this owner
  it will prevent multiple jobs to enter the stack. 
  Instead it will re-use a running job, signal it to stop
  and allow caller to re-initialize it even.
- Check new wm_jobs.c for more explanation. Jobs API is still
  under construction. 
  Fun: BLI_addtail(&wm->jobs, steve); :)

Put Node shader previews back using wmJobs
- Preview calculating is now fully threaded (1 thread still)
- Thanks to new event system + notifiers, you can see 
  previews update even while dragging sliders!
- Currently it only starts when you change a node setting.

Warning: the thread render shares Node data, so don't delete
nodes while it renders! This topic is on the todo to make safe.

Also:
- bug in region initialize (do_versions) showed channel list in
  node editor wrong.
- flagged the channel list 'hidden' now, it was really in the
  way! This is for later to work on anyway. 
- recoded Render API callbacks so it gets handlers passed on, 
  no globals to use anymore, remember?
- previewrender code gets now so much nicer! Will remove a lot
  of stuff from code soon.

source/blender/windowmanager/WM_api.h

@@ -36,9 +36,13 @@ struct IDProperty;
 struct wmEvent;
 struct wmEventHandler;
 struct wmGesture;
+struct wmJob;
+struct wmNotifier;
 struct rcti;
 struct PointerRNA;
 
+typedef struct wmJob wmJob;
+
 /* general API */
 void		WM_setprefsize		(int stax, int stay, int sizx, int sizy);
 
@@ -168,5 +172,18 @@ void		wmOrtho2			(float x1, float x2, float y1, float y2);
 void		WM_set_framebuffer_index_color(int index);
 int			WM_framebuffer_to_index(unsigned int col);
 
+			/* threaded Jobs Manager */
+
+struct wmJob *WM_jobs_get(struct wmWindowManager *wm, struct wmWindow *win, void *owner);
+
+void		WM_jobs_customdata(struct wmJob *, void *customdata, void (*free)(void *));
+void		WM_jobs_timer(struct wmJob *, double timestep, unsigned int note);
+void		WM_jobs_callbacks(struct wmJob *, 
+							  void (*startjob)(void *, short *, short *),
+							  void (*listener)(struct wmJob *, struct wmNotifier *), 
+							  void (*update)(void *));
+
+void		WM_jobs_start(struct wmJob *);
+
 #endif /* WM_API_H */