Merge from origin/emacs-27

Merge from origin/emacs-27

5280e118c0 (origin/emacs-27) ; * src/xdisp.c (pos_visible_p): Fix las...
bb1a9481c9 Fix posn-at-point at beginning of a display string
0c4b033670 Improve documentation of Info node movement commands
632b0119e1 Add Jansson dependency to Windows Build
dbfcdab837 Unbreak 'reverse-region'
c37de84845 Fix typos and markup in fill column indicator docs
f61bff3ee9 ; * CONTRIBUTE: Clarify the preferences for patch formatting.
368e140660 Avoid crashes in 'defconst'
11e3413cff Fix text about Lisp archives in the Emacs FQ
4c81724675 Don't use 'cl' functions in ELisp manual's examples