[Orgmode] Feature request: custom clock headings

[Tom Weissmann]

Many of my subtasks have the same name, so the current modeline isn't always
very useful - if I'm working on a particular bug it might tell me 
"[1:20 Reproduce the error]", 
whereas I'd prefer it to say 
"[1:20 Bug #12303 Disappearing accounts ... Reproduce the error]"

Could we have the option to create a custom function to create clock headings?

Eg, somewhere in `org-clock-in':

...
(if org-custom-clock-heading
  ;; custom clock heading
  (funcall org-custom-clock-heading)
  ;; business as usual
  (if (looking-at org-todo-line-regexp)
    (setq org-clock-heading (match-string 3))
...