We already have these checks in many printf-type functions that have
prototypes which are in header files.  Add these same checks to some
more prototypes in header functions and to static functions in .c
files.

cc: Miklos Vajna <vmiklos@frugalware.org>
Signed-off-by: NTarmigan Casebolt <tarmigan+git@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>