All e-commerce price-related actions fail with missing function format_currency

When attempting to view a product I get

Call to undefined function format_currency() in /usr/www/drupal.lazarusid.com/sites/all/modules/ecommerce/product/product.module on line 1838

When I attempt to enter ecommerce configuration I get the same error.

Where is this mysterious format_currency function defined, and when will it be available in your releases? As the ecommerce project currently stands it is not usable, which is a bad situation for any project to be in. Both the stable release and the development snapshot produce this broken situation. Awkward when everyone just received a security notice telling us to upgrade to the latest version of e-commerce.