Remove node_gallery_api_taxonomy_compare()

In one of my sites that had been upgraded from D6, I was getting an undefined function error for taxonomy_preview_terms() on line 996 of node_gallery_api.inc. It looks like taxonomy_preview_terms() was indeed removed in D7, but this problem was only showing up on my site because my upgrade from D6 had left intact my list of fields that are included on the bulk editing screen, including the "taxonomy" field, which no longer exists in D7.

Node Gallery appears to have special processing built in for taxonomy, which used to be a combined field for all vocabularies. In D7, it's just a field like everything else. So it seems like node_gallery_api_taxonomy_compare() and it's calling code can be removed.

Code to be removed:

    // special case for taxonomy, as its representation
    // in form_state is different than in the node object.
    if ($f == 'taxonomy') {
      if (node_gallery_api_taxonomy_compare($old_image, $new_image)) {
        return TRUE;
      }
      else {
        continue;
      }
    }

Plus all of node_gallery_api_taxonomy_compare() itself.