Describe recent changes in window code and provide some examples.

Describe recent changes in window code and provide some examples.

* windows.texi (Windows and Frames): Provide example of
combinations.
(Resizing Windows): Rewrite description of
adjust-window-trailing-edge.
(Splitting Windows): Provide examples how splitting affects
internal windows.  Rewrite description of window-splits.
(Deleting Windows): Rewrite description of delete-windows-on.
(Displaying Buffers): Describe fun-with-args specifier.
Describe display-buffer-alist-set.
(Window Configurations): Describe window-state-get and
window-state-put.