(gnus) Allow gnus-retrieve-headers to return headers directly

[Madhu]

Hello, I believe gnus commit 20add1cd22f977 has introduced some unwanted
behaviour. Let me describe an example: Assume I have a Group buffer line
for a foreign group like:

269: nntp+news.aioe.org:alt.quotations

I enter this group I arrange for it to ask me how many articles to
read: How many articles: Say I enter 20, I expect to see the last 20
messages (unread and ticked).

In this case I have 16 unread messages and 4 ticked articles, so I'd
see a mode line in the Summary buffer like

-UUU:@----F2  news:a.quotations [0] {16(+253) more}   89% L323   (Summary 
Plugged)  ---

and the Summary buffer would display only 20 lines.

However all ticked and cached articles are inserted in the Summary
buffer. So in this case I have some 400 Summary lines, while it should
have been only 20.  Can anyone confirm this regression?