Enable date-formatting overrides

[lat9]

The current date formatting uses definitions which "should" be overridable via a store-specific extra_datafiles module:

$time_display = (strtolower(DATE_FORMAT) == 'd/m/y') ? 'n-j-Y' : 'jS-M-y';
define('TIME_DISPLAY_DAY', $time_display);
define('TIME_DISPLAY_WEEK', $time_display);
define('TIME_DISPLAY_MONTH', $time_display);
define('TIME_DISPLAY_YEAR', $time_display);