currency_api.module should not use t() in hook_install()

Issue Summary

Modules should not be using t() in hook_schema. For more details, see these notes about When to use st(), t() and get_t() in install and update functions.

For a number of reasons (see http://drupal.org/node/332123), including website performance and the desire avoid encouraging translators to spend time on work of possibly limited value, Drupal 7 and also Drupal 6.9 and later no longer use t() on these strings. You should include schema table and field descriptions as verbatim strings without wrapping them in localization code.