* doc/emacs/m-x.texi (M-x): Index 'M-X'.
* doc/lispref/commands.texi (Interactive Call, Command Modes):
Mention 'M-X' and 'execute-extended-command-for-buffer'.
* etc/NEWS: Clarify that the '(declare (completion ...' and
'(declare (modes ...' forms have no effect by default. Likewise
for '(interactive "..." MODE)' specs. (Bug#52839)