Handle multiple desktop files in different dirs.

Handle multiple desktop files in different dirs.
Other cleanups.
Command line option --no-desktop introduced.
(desktop-read): Record buffers in the desktop file in
the same order as that in the buffer list,
(desktop-save): Put buffers in the order given in desktop file,
regardless of what handlers do.
(desktop-file-version): New variable. Version number of desktop
file format.
(desktop-create-buffer-form): Variable deleted.
(desktop-save): New customizable variable.
(desktop-kill): Changed to use `desktop-save'.
(desktop-file-name-format): New option: format in
which desktop file names should be saved.
(desktop-file-name): New function to convert a filename to the
format specified in `desktop-file-name-format'.
(desktop-create-buffer): Parameters renamed to descriptive
systematic names. These parameters are visible to handlers.
Renames:
ver    -> desktop-file-version
mim    -> desktop-buffer-minor-modes
pt     -> desktop-buffer-point
mk     -> desktop-buffer-mark
ro     -> desktop-buffer-read-only
locals -> desktop-buffer-locals
(desktop-buffer-major-mode, desktop-buffer-file-name)
(desktop-buffer-name): Unused customizable variables deleted.
(desktop-buffer-misc): Unused variable deleted.
(desktop-save, desktop-buffer-dired-misc-data):
Use `desktop-file-name'.
(desktop-path): New customizable variable.  List of directories in
which to lookup the desktop file. Replaces hardcoded list.
(desktop-globals-to-clear): New variable replaces hardcoded list.
(desktop-clear-preserve-buffers-regexp): New customizable variable.
(desktop-after-read-hook): New hook run after a desktop is read.
(desktop-no-desktop-file-hook): New hook when no desktop file found.
(desktop-change-dir): New function.
(desktop-save-in-load-dir): New function. Save desktop in
directory from witch it was loaded.
(desktop-revert): New function. Revert to the last loaded desktop.