Bug 12976: Use the centralize VAT and prices calculation - invoice.pl

Bug 12976: Use the centralize VAT and prices calculation - invoice.pl

Bug 12969 introduces a subroutine to centralize VAT and prices
calculation.
It should be use in the acqui/invoice.pl script.

Test plan:
0/ Don't apply the patch
1/ Create 4 suppliers with the different configurations
2/ Create a basket and create several orders
3/ Receive the items and create an invoice
4/ Go on the invoice page acqui/invoice.pl?invoiceid=XXX
5/ Verify you don't see any difference before and after applying the
patch on the invoice details table.
Note: The only different you should see is the price formating for
"Total tax exc.". Before this patch "432.10" was displayed "432.1".

Signed-off-by: Paola Rossi <paola.rossi@cineca.it>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>