Merge changes made in Gnus trunk:

nnml.el (nnml-save-nov): Remove some debugging-related messages.

gnus-start.el (gnus-read-active-for-groups): Do a `gnus-request-scan' for the methods that support -retrieve-groups, too.

gnus-html.el (gnus-html-wash-tags): Remove <a name...> tags, which confuses the rest of the function.

gnus-start.el (gnus-get-unread-articles): If being given an explicit level to get unread articles from, then use that for foreign groups, too.

nntp.el (nntp-wait-for-string): Supply a timeout for accept-process-output to ensure progress.

gnus-async.el (gnus-async-article-callback): Always prefetch images for groups that want that.

gnus-html.el (gnus-html-wash-tags): Limit end-tag matching to the current line to work around bugs in the output from w3m.