[O] C-c C-y in currently clocked header

[Daniel Clemente]

Feature request.

**** currently clocking
         :CLOCK:
         CLOCK: [2014-10-15 Wed 16:06]
         CLOCK: [2014-10-13 Mon 11:23]--[2014-10-13 Mon 11:54] =>  0:31
         :END:

Now it's 16:26. If I put the cursor in 16:06 and press C-c C-y 
(org-evaluate-time-range), it would be useful to see in the minibuffer that the 
difference until now is 20 minutes.