bug#63595: 30.0.50; ERC 5.6: Add buffer-list and nick-list modules

[J.P.]

It's been reported that the nickbar (speedbar) window doesn't display
the cursor on at least one user's setup. I've found this to be true by
default on non-graphic displays. The attached patch should fix the
latter regression. As to whether it also fixes the reporter's issue is
TBD.

It's also been reported that the dframe timer can signal a

  (wrong-type-argument window-live-p nil)

which then gets trapped by the

  (with-demoted-errors "DFRAME TIMER ERROR: %S"...)

in `dframe-timer-fn'. Unfortunately, remediation is trickier here
because we've got to inspect calls to `window-live-p' stemming from
`speedbar-timer-fn', possibly via `erc-speedbar-insert-user'. (What we
really need is a backtrace from the bug reporter.)

0001-5.6-Fix-invisible-erc-speedbar-cursor-in-text-termin.patch
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