Search display modes

Issue Summary

While digging into sphinxsearch, I found that it's using NODE_BUILD_SEARCH_INDEX and NODE_BUILD_SEARCH_RESULT node build modes for index building. As you may know CCK 2.0 gives ability to setup it's fields according to specific node build mode. But search build modes can only be configured when drupal's search module is enabled. It's because CCK overides it's own hook instead search module in function search_content_build_modes(). As it's a hook, it doesn't executes while search module is disabled.

With using sphinx search there are no need to have search module at all, but there is a strainght need to make settings to CCK fields in search. So, it will be nice if sphinxsearch will implement hook_content_build_module() instead of search module.

I created the patch which allow to do so. Thanks for review.