bug#10539: 24.0.92; low display-time-interval makes Emacs slow

[Glenn Morris]

Eli Zaretskii wrote:

> Would the following wording make it less confusing/contradictory?
>
>   Force next redisplay cycle to update the current buffer's mode line
>   and header line, based on the latest values of all the relevant
>   variables.

Yes thanks. Plus something similar for the function's doc-string.
So it doesn't actually "force redisplay", it just marks things to be
updated the next time redisplay happens to occur (?).