Include dlfcn.h.

Include dlfcn.h.
(Mword): New variable.
(show_cursor): Check Mlanguage text property of the cursor
position only.
(delete_char): Pay attention to the change of line beginning
position because of filling.
(insert_chars): Likewise.
(word_constituent_p, forward_word, backward_word): New functions.
(KeyProc): Assign XK_b and XK_f for back/foreward word.
(line_break): Delete extern.
(LineBreakProc): Use mdraw_default_line_break.
(FilterProc): New function.
(main): Handle --filter arg.  Initialize Mword.