tune2fs.c: Changed the external journal code so that it simply adds a
filesystem to a journal; the journal must have bene created via
"mke2fs -O journal_dev /dev/XXX".
mke2fs.c: Add support for creating an external journal device by using
the command "mke2fs -O journal_dev /dev/XXX". Also changed the
external journal code so -j device=/dev/XXX it simply adds a
filesystem to that journal; the journal must have been created via
separate step.
dumpe2fs.c (print_journal_information): Add support for dumping
information about an external journal device.