Adapt the call to theme('freelink_error') to new conventions used in Drupal 7

According to this recommendation -

all theme calls should now use one array parameters

- I think we should adapt the call to theme('freelink_error') to new conventions.

at this time the call is implemented as:

function freelinking_get_freelink($plugin, $target, $format = 'all', $rendered = TRUE) {
  ...
  theme('freelink_error', array($plugin, $link['message']));
  ...
}

We should change it to:

function freelinking_get_freelink($plugin, $target, $format = 'all', $rendered = TRUE) {
  ...
  theme('freelink_error', array('plugin' => $plugin, 'message' => $link['message']));
  ...
}

So the message will be available inside of hook implementation:

function theme_freelink_error($variables) {
  $plugin  = $variables['plugin'];
  $message = $variables['message'];
  ...
}