Merge from origin/emacs-27

74a77ef299 Improve documentation of 'network-lookup-address-info'
c6d5555646 Display messages sent using ERC's /say
c156723769 Fix Rmail summary display when From: header is malformed

diff --cc doc/lispref/processes.texi
Simple merge

diff --cc lisp/erc/erc.el
Simple merge

diff --cc lisp/mail/rmailsum.el
Simple merge

diff --cc src/process.c
Simple merge