Fixed #16897 -- Fixed some docstrings and help texts for the `makemessages`...

Fixed #16897 -- Fixed some docstrings and help texts for the `makemessages` management command. Thanks, Simon Meers.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16864 bcc190cf-cafb-0310-a4f2-bffc1f526a37