Create a nodecomment_get_comment_type() function

If we had a function nodecomment_get_comment_type($node_type) then advanced forum could simply use $comment_type = module_invoke('nodecomment', 'get_comment_type', $node->type);

if $comment_type is set, it is using node comments. If not, it isn't.

This will make it easy to do switches to nodecomment from external sources for doing their queries or getting data about comments.