Merge from origin/emacs-27

Merge from origin/emacs-27

2f9bfaef21 (origin/emacs-27) ; Fix last change
520fd3e728 * lisp/env.el (substitute-env-vars): Doc fix.  (Bug#40948)
85544f8ef5 * lisp/isearch.el: Fix lazy-highlighting and lazy-counting...
d83cc05a73 Fix error in ERC when 'erc-server-coding-system' is custom...
16fed05ba8 Avoid crashes on TTY frames with over-long compositions
0278741676 Fix typo in custom.texi
9f5ae717fb * test/lisp/simple-tests.el (with-shell-command-dont-erase...
1f76a16ed3 * lisp/image-mode.el (image-mode-map): Update menu items.
f0e1bf56f0 Fix bugs in tab-bar and tab-line and mention remaining fea...
f0b9f18457 Make shell-command tests fit for tcsh.
68f4a740a1 Remove doc duplication
ac31cd384c * etc/NEWS: Fix inconsistencies.

# Conflicts:
#	etc/NEWS