Done backport of 6.x-1.2 to Drupal 5

Nice work, Maciej. I needed this module for an older Drupal 5 site, along with plugin implementation, so I did a pretty basic backport of 6.x-1.2 version to Drupal 5. The code edits concern implementations of hook_menu and googleajaxsearch_settings_validate(), so it was a pretty light job. I have tested it, along with a custom plugin, no issues so far. Here it is, in case somebody needs it or if you may want to sync the Drupal 5 branch at some point.