[IMP] account: improve performances of computation of the two fields due_delay and delay_to_pay for account_invoice_report
[IMP] account: improve performances of computation of the two fields due_delay and delay_to_pay for account_invoice_report

lp bug: https://launchpad.net/bugs/1000195 fixed

bzr revid: mat@openerp.com-20131004092309-5ni48mpupfcms181
podemos-info/odoo,podemos-info/odoo,podemos-info/odoo,podemos-info/odoo,podemos-info/odoo,podemos-info/odoo,podemos-info/odoo