* lisp/erc/erc.el (erc--update-cusr-status-if-changed): Remove unused
macro.
(erc-update-current-channel-member): Redo doc string and abide by its
original language to the letter by not honoring a value of t for the
five channel-membership status parameters, even though this may break
user code that accidentally passes t instead of `on'. Avoid double
lookup for nick in `erc-server-users'. Rename some variables as per
recommended conventions for `erc-channel-user' objects. Stash
downcased nick for further reuse. Don't bother factoring in `addp' to
return value because `cusr-changed-p' is always non-nil when `addp'
is.