hexdump: color unit may now be longer than the corresponding format unit

Signed-off-by: Ondrej Oprala <ooprala@redhat.com>
logger: allow user to send structured journald messages

This feature is hopefully mostly used to give MESSAGE_ID labels for
messages coming from scripts, making search of messages easy.  The
logger(1) manual page update should give enough information how to use
--journald option.

[kzak@redhat.com: - add missing #ifdefs
                  - use xalloc.h]

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
Signed-off-by: Karel Zak <kzak@redhat.com>