Bug 12229: when exporting MARC records (as ISO2709), refuse to output records that...

Bug 12229: when exporting MARC records (as ISO2709), refuse to output records that would be longer than the MARC limit

Test:
1. Edit a bib record, add 100.000 chars text to 500a
2. Go to Tools -> Export data (or run tools/export.pl on
   the command line)
3. Verify that exporting as XML includes the record
4. Verify that exporting as MARC does not include the record,
   and that you get the following warning:

export.pl: record (number 2025) length 102668 is larger than the MARC spec allows (99999 bytes) at...

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Work as described. No errors

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit 1f72a1c2dd45c3a570746dd575b0fcfb38d13dc4)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>