Add @kindex in manuals for existing keybindings on 'C-x x/w' (bug#13167)

Add @kindex in manuals for existing keybindings on 'C-x x/w' (bug#13167)

* doc/emacs/buffers.texi (Misc Buffer): Add @kindex for 'C-x x r',
'C-x x u', 'C-x x i'.

* doc/emacs/display.texi (Line Truncation): Add @kindex for 'C-x x t'.

* doc/emacs/files.texi (Reverting): Add @kindex for 'C-x x g'.

* doc/emacs/windows.texi (Change Window): Use new keybinding 'C-x w 0'
instead of 'M-x delete-windows-on'.

* doc/misc/info.texi (Create Info buffer): Add @kindex for 'C-x x n'.

(cherry picked from commit 51f391998b19a94d35d743952006afd71ad7f545)