No CHANGES entry for this as it isn't proved to cause an issue for
anyone (isc_msgcat_get() has to return a format specifier) and isn't a
user visible change.

Squashed commit of the following:

commit bcb15c9aa17b0b706aefd9efef5f7e0e951064a3
Author: Mukund Sivaraman <muks@isc.org>
Date:   Wed Jun 4 16:55:16 2014 +0530

    [27303] Supply format string as first arg to printf()

    The old code only had a problem if isc_msgcat_get() returned a format
    specifier (%n).