Use macros from dispextern.h where appropriate.

Use macros from dispextern.h where appropriate.

 src/xdisp.c (display_tool_bar_line, redisplay_tool_bar)
 (redisplay_internal, set_cursor_from_row, try_window)
 (try_window_id, dump_glyph_row, extend_face_to_end_of_line)
 (display_line, notice_overwritten_cursor)
 (mouse_face_from_buffer_pos, note_mouse_highlight): Use
 MATRIX_ROW_DISPLAYS_TEXT_P.
 (note_mouse_highlight): Use MATRIX_ROW_GLYPH_START.
 (mouse_face_from_string_pos, fast_find_string_pos): Use
 MATRIX_ROW_VPOS.
 src/xfns.c (Fx_show_tip): Use MATRIX_ROW_DISPLAYS_TEXT_P.
 src/w32fns.c (Fx_show_tip): Use MATRIX_ROW_DISPLAYS_TEXT_P.
 src/xdisp.c (try_cursor_movement): Use MATRIX_ROW and
 MATRIX_MODE_LINE_ROW.
 src/dispnew.c (update_window): Use MATRIX_ROW and MATRIX_MODE_LINE_ROW.