Adding filters for Recent Comments Widget

[hovenko]

The attached patch adds two filters called "comments_join" and "comments_where" to alter the SQL statement for the Recent Comments widget.

Maybe it's time for a comments API?

I see that the cache was not cleared when new comments were written. Applying a new patch.

Adds filters for distinct, join and where to recent comments.

Currently the recent comments widget uses a SELECT * which is a change from the version that the attached patch was created against.

Consequently this would have to be re-done, in case limiting the output to just the fields in the patch breaks other functionality.

As an aside, selecting either * or comment_id, comment_post_id would always be DISTINCT so the keyword is not required.

see also #9211

you can now override the widget's callback entirely.