bug#12708: 24.1; M-x display-time-world "q" close window

[Glenn Morris]

Chong Yidong wrote:

> Yes, display-time-world is clearly behind the times, and the use of
> pop-to-buffer is a mistake.  I changed display-time-world-mode to derive
> from special mode, and display-time-world to use display-buffer.

emacs -Q -f display-time-world
q    ; in world time buffer
M-x display-time-world
   -> Buffer is read-only: #<buffer *wclock*>