(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-globals-to-save): Variable made customizable.
(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.