Various window code related fixes and documentation changes.

Various window code related fixes and documentation changes.

* dispnew.c (change_frame_size_1): Add new_lines instead of
new_height, the latter may be still zero if passed as such.
* window.c (Fwindow_pixel_height): Mention bottom divider in
doc-string.
* window.el (window-min-height, window-min-width): Rewrite
doc-strings.
(window-body-size): Add PIXELWISE argument to make it consistent
with its callees.
* display.texi (Window Dividers): New section.
* frames.texi (Layout Parameters): Add right-divider-width and
bottom-divider-width.
* windows.texi (Window Sizes): Redraw schematic and rewrite its
description.  Rewrite descriptions of `window-total-height',
`window-total-width', `window-total-size', `window-body-height',
`window-body-width' and `window-size-fixed'.  Add descriptions
for `window-pixel-height', `window-pixel-width',
`window-min-height' and `window-min-width'.  Remove description
of `window-size-fixed-p' moving part of it to that of
`window-size-fixed'.
(Resizing Windows): Mention dividers when talking about minimum
sizes.