[FIX] Account: performance account_move_line needs index on partner_id

lp bug: https://launchpad.net/bugs/571595 fixed

bzr revid: mra@mra-laptop-20101116041416-zonccm8lg9dvf2at

addons/account/account_move_line.py

@@ -436,7 +436,7 @@ class account_move_line(osv.osv):
         'period_id': fields.many2one('account.period', 'Period', required=True, select=2),
         'journal_id': fields.many2one('account.journal', 'Journal', required=True, select=1),
         'blocked': fields.boolean('Litigation', help="You can check this box to mark this journal item as a litigation with the associated partner"),
-        'partner_id': fields.many2one('res.partner', 'Partner'),
+        'partner_id': fields.many2one('res.partner', 'Partner', select=1),
         'date_maturity': fields.date('Due date', help="This field is used for payable and receivable journal entries. You can put the limit date for the payment of this line."),
         'date': fields.related('move_id','date', string='Effective date', type='date', required=True,
                                 store = {