date_field_get_sql_handler() removal broke Signup-7.x-1.x-dev

Removing date_field_get_sql_handler() from Date has broken signup-7.x-1.x-dev.

In signup/includes/date.inc the API is used by:

function _signup_date_reminder_sql($content_type) {
  // Get the date field information for this content type.
  $field = signup_date_field($content_type);
  $start_field = $field['field_name'] . '_value';

  // Figure out what TZ we want to do the date comparisons in.
  $compare_tz = $field['settings']['tz_handling'] == 'none' ? date_default_timezone() : 'UTC';
  // Get a DateAPI SQL handler class for this field.
  $handler = date_field_get_sql_handler($field, $compare_tz);

  // Find the current time in the appropriate TZ for this field.
  $now_date = date_now($compare_tz);
  // Need to enclose this in ' marks to use directly in the SQL.
  $now = "'" . date_format($now_date, DATE_FORMAT_DATETIME) . "'";

  // Extract the correct SQL to represent the start time.
  $start_time = $handler->sql_field($start_field);
...