Monetary amount multiplied by 100 in contribution form - error in other amount validation

Reproduced in demo site (http://drupal.demo.civicrm.org/civicrm/admin/contribute?reset=1) :

• in civicrm/admin/setting/localization?reset=1, put nothing in Thousands Separator and . (period) in Decimal Delimiter
• use a contribution form like civicrm/contribute/transact?reset=1&id=1 and set 10,00 (comma) in the amount
• in the confirmation page, the amount display 1000.00 instead of triggering an error (comma is not an option in our case)

It causes problems as user doesn't always read carefully the confirmation page and pay 100 times more than he expected.
We should fix this by validating the amount before going to the confirmation page and display the expected amount format.