Add text format specific 'rlocn' ignore flag and access functions.

Add text format specific 'rlocn' ignore flag and access functions.

Adding a flag to the 'rlocn' structure in the mda header of the
text format allows us to flip a bit to ignore an area on disk that
stores the metadata via the text format specific mda_header.
This patch defines the flag and access functions to manage the flag.
Other patches will manage the ignore on a format-independent basis,
by using a flag in the metadata_area structure.

Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>