[trunk] l10n_nl: wrong tax reporting of intracom purchases

Hi,

When purchasing inside EU from an entity that is liable for the purchase's VAT in its own country, the Dutch chart of accounts creates a negative and a positive tax entry for the same amount adding up to an amount of €0,00 on the invoice. On the report, however the amount to pay due to the purchase is not €0,00 but double the tax amount. Additionaly, the negative entry is on the account where a positive entry is registered in case of a domestic purchase and vice versa.

Steps to reproduce:
Install a database and configure the Dutch charts of accounts. Create a supplier invoice of €1,00 with tax "19% BTW import binnen EU" on the invoice line. Validate the invoice.

Current results:
Account "Btw af te dragen hoog/tax payable" is debited with € 0, 19
Account "Btw te vorderen hoog/tax receivable" is credited with € 0,19
Tax report shows a total amount of tax to pay of € 0,38.

Expected result:
Account "Btw af te dragen hoog/tax payable" is credited with € 0, 19
Account "Btw te vorderen hoog/tax receivable" is debited with € 0,19
Tax report to show a total amount of tax to pay of € 0,00

Best regards,
Stefan