image.c, indent.c: Use bool for booleans.

image.c, indent.c: Use bool for booleans.

* dispextern.h (struct image_type): Members valid_p, load, init
now return bool, not int.  All uses changed.
* image.c: Omit unnecessary static decls.
(x_create_bitmap_mask, x_build_heuristic_mask):
Return void, not int, since callers don't care about the return value.
(x_create_bitmap_mask, define_image_type, valid_image_p)
(struct image_keyword, parse_image_spec, image_spec_value)
(check_image_size, image_background)
(image_background_transparent, x_clear_image_1)
(postprocess_image, lookup_image, x_check_image_size)
(x_create_x_image_and_pixmap, xbm_image_p)
(Create_Pixmap_From_Bitmap_Data, xbm_read_bitmap_data)
(xbm_load_image, xbm_file_p, xbm_load, xpm_lookup_color)
(init_xpm_functions, xpm_valid_color_symbols_p, xpm_image_p)
(xpm_load, xpm_load_image, lookup_rgb_color, lookup_pixel_color)
(x_to_xcolors, x_build_heuristic_mask, pbm_image_p, pbm_load)
(png_image_p, init_png_functions, png_load_body, png_load)
(jpeg_image_p, init_jpeg_functions, jpeg_load_body, jpeg_load)
(tiff_image_p, init_tiff_functions, tiff_load, gif_image_p)
(init_gif_functions, gif_load, imagemagick_image_p)
(imagemagick_load_image, imagemagick_load, svg_image_p)
(init_svg_functions, svg_load, svg_load_image, gs_image_p)
(gs_load):
* nsimage.m (ns_load_image):
* nsterm.m (ns_defined_color):
* xfaces.c (tty_lookup_color, tty_defined_color, defined_color):
* xfns.c (x_defined_color):
* xterm.c (x_alloc_lighter_color_for_widget)
(x_alloc_nearest_color_1, x_alloc_nearest_color)
(x_alloc_lighter_color):
* indent.c (disptab_matches_widthtab, current_column)
(scan_for_column, string_display_width, indented_beyond_p)
(compute_motion, vmotion, Fvertical_motion):
Use bool for booleans.