Rewrites of Elisp manual including tab-bar and tab-line changes

Rewrites of Elisp manual including tab-bar and tab-line changes

* doc/lispref/buffers.texi (Current Buffer, Buffer List): Update
references to 'selected-window'.
* doc/lispref/elisp.texi (Top): Move up Selecting Windows section
in front of Window Sizes section.
* doc/lispref/frames.texi (Creating Frames): Say window system
instead of windowing system.
(Frame Layout): Add Tab Bar to layout.
(Layout Parameters): Add 'tab-bar-lines'.
(Input Focus): Say window system window instead of window
manager window.  Fix reference to 'selected-window'.
* doc/lispref/objects.texi (Window Type): Minor rewrite.
* doc/lispref/windows.texi (Basic Windows): Rewrite.  Settle on
term 'window system window' for disambiguation with our windows.
Move 'selected-window' description to Selecting Windows section.
Move schematic of window structure here.  Use 'decorations' for
objects outside the window body.  Say that the areas reserved
for continuation and truncation glyphs, vertical dividers and
line numbers are part of the window body.
(Windows and Frames): Minor rewrite, adding and fixing some
cross references.  Move live window schematic to 'Basic Windows'
section.
(Selecting Windows): Move section in front of Window Sizes
section.  Move description of 'selected-window' here.  Move up
description of 'frame-selected-window' and
'set-frame-selected-window'.  Update and move description of
'window-bump-use-time' here.
(Window Sizes): Throughout use the term 'decorations' instead of
enumerating them individually.  Add 'window-tab-line-height'
description.
(Resizing Windows): Again use the term 'decorations' instead of
enumerating them individually.
(Splitting Windows): Minor fix.
(Cyclic Window Ordering): Improve descriptions of 'get-lru-window'
and 'get-mru-window'.  Move 'window-bump-use-time' to Selecting
Windows section.
(Coordinates and Windows, Window Configurations): Once more use
the term 'decorations' instead of enumerating them individually.
* src/window.c (Fwindow_bump_use_time): Move after
'window-use-time'.  Make it work for live windows only.  Make
WINDOW argument optional.  Update doc-string.