Retrospective commit from 2009-10-03.

Retrospective commit from 2009-10-03.

Detect paragraph start and paragraph separators (part of determining
paragraph base direction).

(The commit of window.h belongs to the original changes by Kenichi Handa,
it was forgotten earlier.)

 bidi.c (bidi_set_paragraph_end): Don't set the new_paragraph
 flag in the iterator.
 (bidi_init_it): Set the new_paragraph flag.
 (bidi_at_paragraph_end): Arguments are now character and byte
 position of the next character.  All callers changed.
 (bidi_resolve_explicit): Don't call bidi_at_paragraph_end, and
 don't behave as if at paragraph end if it returns true.
 (bidi_get_next_char_visually): Don't call bidi_paragraph_init if
 new_paragraph flag is set.  Set new_paragraph flag when at end of
 a paragraph.
 <fallback_paragraph_start_re, fallback_paragraph_separate_re>: New
 variables.
 <Qparagraph_start, Qparagraph_separate>: New variables.
 (bidi_initialize): Initialize and staticpro them.
 dispextern.h <struct bidi_it>: New element paragraph_dir.  Make
 positional elements EMACS_INT.
 bidi.c <bidi_overriding_paragraph_direction>: Delete.