put message in do_quote(), do_set_mark(),
added find_window() to locate window in a given direction.
added do_previous_window() for window navigation.
do not split popup window in do_split_window().
allow window navigation with C-X n / C-X p /
C-X up / C-X down / C-X left and C-X right.
added BUFED_ALL_VISIBLE flag to include system buffers in list
display buffer size
added bufed_clear_modified, bufed_toggle_modified.
added bufed_toggle_all_visible, navigation keys.
improved dired mode:
store file details in separate structure
added sorting options, marking options
