[IMP] l10n_es_vat_book: fix performance issue (#984)
[IMP] l10n_es_vat_book: fix performance issue (#984)

When a large amount of move lines are processed (hundreds of thousands)
it can lead to a MemoryError when we try to calculate the VAT book
factorlibre/l10n-spain,factorlibre/l10n-spain,factorlibre/l10n-spain