fiscal year across two calendar years block accounting config

[V V Dyck]

* Using Trunk via deb depots on fresh updated Ubuntu 12.04 server (INFO ? openerp: OpenERP version 7.0-20130130-000102)
* Using Firefox 18.0.1 on an Ubuntu 10.04 desktop

Steps:
* Empty database (US) without demo-data and minimal profile.
* Install 'Accounting and Finance' module
* In the 'Configure Accounting Data' wizard,
          choose for 'Accounting Package' : Belgium - Accounting
          choose for 'Date Range' : 04/01/2012 and 03/31/2013
          choose for 'Periods' : 3 monthly
* Go to 'Settings | Configuration | Accounting', check 'Allow pro-format invoices' and 'Apply' leads to :

*************************
OpenERP Warning

ValidateError

Error occurred while validating the field(s) date_stop: Error!
The period is invalid. Either some periods are overlapping or the period's dates are not matching the scope of the fiscal year.
*************************

* abort change
* Go to 'Accounting | Configuration | Periods | Fiscal Years' and choose the '12-13' fiscal year
* Erase periods
* Change start and end dates for 01/01/2012 and 12/31/2012
* Populate with 'Create 3 Months Periods' and save
* Go to 'Settings | Configuration | Accounting', check 'Allow pro-format invoices' and 'Apply' is OK now.
* Do again the opposite brings error back

Remarks :
* Not tested with other 'Accounting Package', but tested with 'custom set' : same behaviour
* Seems to have same behaviour while changing anything in 'Settings | Configuration | Accounting'