Emacs 28 stragglers

[J.P.]

This is a list of candidates for last-minute inclusion in Emacs 28.

The leading numbers are a crude attempt at approximating the relative
cost of closing out each item. They assume, among other things, a
consistent degree of reviewer familiarity across ERC. The selection and
the ordering were gleaned (perhaps incorrectly) from some maintainerly
wisdom shared in #erc. Corrections welcome.

2 Track: Modified channels doc and `erc-track-find-face' fixes
  https://debbugs.gnu.org/cgi/bugreport.cgi?bug=46775

2 NickServ identification: Prompt for password after other sources,
  overall simplifications
  https://debbugs.gnu.org/cgi/bugreport.cgi?bug=46777

2 Allow IRC network symbols in erc-autojoin-channels-alist
  https://lists.gnu.org/archive/html/emacs-devel/2015-03/msg00088.html
  https://lists.gnu.org/archive/html/emacs-devel/2018-02/msg00664.html
  https://github.com/unhammer/emacs/commit/4c0075db

2 Backport or replace 28-only string-* functions
  https://git.savannah.gnu.org/cgit/emacs.git/commit/?id=3b7b181bde 
  https://git.savannah.gnu.org/cgit/emacs.git/commit/?id=051434fdef  

1 Silence a couple byte-compiler warnings
  https://debbugs.gnu.org/cgi/bugreport.cgi?bug=50005

1 Add CRLF to outgoing protocol logger lines
  https://debbugs.gnu.org/cgi/bugreport.cgi?bug=50009

1 Be less presumptuous with announced server names
  https://debbugs.gnu.org/cgi/bugreport.cgi?bug=50010

2 Normalize logic surrounding erc-server-reconnecting
  https://debbugs.gnu.org/cgi/bugreport.cgi?bug=50007

2 Don't send empty lines with user input
  https://debbugs.gnu.org/cgi/bugreport.cgi?bug=50008