bug 5579 : Fixes several exports to embed items

bug 5579 : Fixes several exports to embed items

  - The following export pages used to embed items when exporting,
    this was no longer the case, so they were fixed :
      Intranet :
        - basket/downloadcart.pl,
        - virtualshelves/downloadshelf.pl
        - catalogue/export.pl
      Opac :
        - opac/opac-downloadcart.pl
        - opac/opac-downloadshelf.pl
        - opac/opac-export.pl

  - Notes :
     - GetMarcBiblio used to embed items data, this was no longer the case,
       so an optional parameter was added to choose if items should be embedded or not.
       This way, previous work on this bug is not broken, and this is a pretty usefull
       feature, imho.
     - An optional parameter has been added to SetUTF8Flag, to be able to use NFD during
       normalization. This was required to make Unicode/UTF-8 export work again.

Signed-off-by: Claire Hernandez <claire.hernandez@biblibre.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>