* common/logging.c (log_printhex): Chnage order of args. Make it
printf alike. Change all callers.
* configure.ac: Add -Wno-format-zero-length
--
This makes it consistent with modern libgpgrt logging and thus eases
back porting from newer GnuPG versions which use libgpgrt logging.
Signed-off-by: Werner Koch <wk@gnupg.org>