[O] Small docstring update

[Stephen Eglen]

Attached is a suggested rewording of the docstring for
org-agenda-prefix-format.



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--- /local/data/home/stephen/langs/emacs/elisp-ds/org-mode/lisp/org-agenda.el   
2013-02-18 14:02:48.731846974 +0000
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*** 1562,1572 ****
  result in a 12 character time field if a time of the day is specified,
  but will completely disappear in entries which do not contain a time.
  
! If there is punctuation or whitespace character just before the final
! format letter, this character will be appended to the field value if
! the value is not empty.  For example, the format \"%-12:c\" leads to
! \"Diary: \" if the category is \"Diary\".  If the category were be
! empty, no additional colon would be inserted.
  
  The default value for the agenda sublist is \"  %-12:c%?-12t% s\",
  which means:
--- 1562,1572 ----
  result in a 12 character time field if a time of the day is specified,
  but will completely disappear in entries which do not contain a time.
  
! If there is punctuation or whitespace character just before the
! final format letter, this character will be appended to the field
! value if the value is not empty.  For example, the format
! \"%-12:c\" leads to \"Diary: \" if the category is \"Diary\".  If
! the category is empty, no additional colon is inserted.
  
  The default value for the agenda sublist is \"  %-12:c%?-12t% s\",
  which means: