[FIX] account.move.line: restore compatibility with RPC calls

Rev. d6e1d41128 removed old API
compatibility layer, but failed to preserve the ability to
call certain public methods from the RPC layer, when extra
browse_record parameters were required.

In particular the @api.v7 version of
`prepare_move_lines_for_reconciliation_widget` was dropped
and there was no way to call it with a `target_currency` RPC
parameter anymore.

addons/account/models/account_move.py

@@ -640,12 +640,16 @@ class AccountMoveLine(models.Model):
     def prepare_move_lines_for_reconciliation_widget(self, target_currency=False, target_date=False):
         """ Returns move lines formatted for the manual/bank reconciliation widget
 
-            :param target_currency: curreny you want the move line debit/credit converted into
+            :param target_currency: currency (browse_record or ID) you want the move line debit/credit converted into
             :param target_date: date to use for the monetary conversion
         """
         context = dict(self._context or {})
         ret = []
 
+        if target_currency:
+            # re-browse in case we were passed a currency ID via RPC call
+            target_currency = self.env['res.currency'].browse(int(target_currency))
+
         for line in self:
             company_currency = line.account_id.company_id.currency_id
             ret_line = {