[O] Prompts for `C-c .' and `C-c !'

[François Pinard]

Hi, Org people! :-)

Commands `C-c .' and `C-c !' both insert a time stamp in the buffer, and
the date is prompted in the mini-buffer in the same way for both
commands.  One of them is going to insert <DATE>, the other [DATE].  The
mini-buffer always show <DATE>, like this:

   Date+time [2012-01-23]:   => <2012-01-23 lun>

Could it be:

   Date+time [2012-01-23]:   => [2012-01-23 lun]

when appropriate?  This feedback would be useful (to me at least), in
case I mixed `C-c .' and `C-c !' in my head, and am using the wrong one.

François