_image_get_sizes instead of _image_get_dimensions for Drupal 5.3

_image_get_dimensions no longer works in Drupal 5.3. Supposedly private api.

I just changed it to _image_get_sizes, but a better solution is below:

See how they resolved it in acidfree:

http://cvs.drupal.org/viewvc.py/drupal/contributions/modules/acidfree/ac...
function _acidfree_get_sizes($size=null) {
if (function_exists('image_get_sizes')) {
return image_get_sizes($size);
}
if (function_exists('_image_get_sizes')) {
return _image_get_sizes($size);
}
if (function_exists('_image_get_dimensions')) {
return _image_get_dimensions($size);
}
return false;
}