Bug 19687: Undefined subroutine in bulkmarcimport

Bug 19687: Undefined subroutine in bulkmarcimport

Bulkmarcimport produces undefined subroutine error for
C4::Items::TransformMarcToKoha and C4::Items::GetMarcStructure
probably caused by mutually recursive modules. Put exports in
BEGIN clause before all the other imports.

To test:
1) Run bulkmarcimport.pl before applying patch and verify
that undefined subroutine error occurs
2) Apply patch
3) Run bulkmarcimport.pl again and verify that no errors are
produced

Sponsored-by: Gothenburg University Library
Signed-off-by: George Veranis <gveranis@gmail.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>