"block author" or "mark author as spam"

Issue Summary

It would be good to be able to take a spam comment, and from there, block the author of the spam. Even better would be to mark the author as a spam-user, and even better would be to mark all content belonging to that author as spam.

This function should be optionally available from the content itself (ie give the user the option to show the link next to the "mark as spam" link), as well as from the admin/content/spam page, in the "update options" drop-down (see also #451946: improvements to admin/content/spam)

This would probably make sense to implement as two separate functions:
spam_block_author($content_type, $content_id)
spam_mark_author_content_as_spam($author_uid)
Marking the user as spam is already done by spam_mark_as_spam()