Bug 16855 - Poor performance due to high overhead of SQL call in export.pl

Bug 16855 - Poor performance due to high overhead of SQL call in export.pl

This patch eliminates all columns retrieved in the biblioitems query
except for biblionumber.

To test:
1 - Go to tools->Export data
2 - Export using various filters and note you get expected records
3 - Apply patch
4 - Ensure exported results match results before patch

Signed-off-by: Srdjan <srdjan@catalyst.net.nz>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit a44bb07b88ba9d5049a64f88610a8bb8e82efe3a)
Signed-off-by: Frédéric Demians <f.demians@tamil.fr>