Include font.h.

Include font.h.
(it_props): Delete the entry for Qauto_composed.
(init_iterator): Initialize it->cmp_it.id to -1.
(compute_stop_pos): Call composition_compute_stop_pos.
(face_before_or_after_it_pos): Adjusted for the change of struct
it.
(handle_auto_composed_prop): Delete it.
(handle_composition_prop): Handle only static composition.
(next_overlay_string): Remove it->method == GET_FROM_COMPOSITION
from xassert.  Initialize it->cmp_it.stop_pos.
(push_it): Adjusted for the change of struct it.
(pop_it): Likewise.
(get_next_element): Delete next_element_from_composition.
(CHAR_COMPOSED_P): New macro.
(get_next_display_element): For automatic composition, get a face
from the font in the glyph-string.
(set_iterator_to_next): For GET_FROM_BUFFER and GET_FROM_STRING,
check composition by it->cmp_it.id.  Delete GET_FROM_COMPOSITION
case.
(next_element_from_string): Check if the character at the current
position is composed by CHAR_COMPOSED_P.
(next_element_from_buffer): Likewise.
(next_element_from_composition): Adjusted for the change of struct
it.  Update it->cmp_it.
(dump_glyph): Adjusted for the change of struct glyph.
(fill_composite_glyph_string): Adjusted for the change of struct
it and struct glyph.  Don't handle automatic composition here.
(fill_gstring_glyph_string): New function.
(x_get_glyph_overhangs): Handle automatic composition.
(BUILD_COMPOSITE_GLYPH_STRING): Adjusted for the change of struct
glyph.
(BUILD_GSTRING_GLYPH_STRING): New macro.
(BUILD_GLYPH_STRINGS): Call BUILD_GSTRING_GLYPH_STRING for
automatic composition.
(append_composite_glyph): Adjusted for the change of struct it and
struct glyph.
(x_produce_glyphs): Adjusted for the change of struct it.