Clean up and simplify image-type setup

This also fixes an unlikely hang involving a circular image
description.
* src/dispextern.h (struct image.type): Now pointer-to-const.
* src/image.c (struct image_type.init) [!WINDOWSNT]: Omit.
(IMAGE_TYPE_INIT): New macro.
(image_types): Now a small array-of-const, not a pointer.
(CACHE_IMAGE_TYPE): Remove; the code’s simpler without it.
(ADD_IMAGE_TYPE): Remove this macro, replacing with ...
(add_image_type): ... this equivalent function.  All uses changed.
(define_image_type): Remove.  All uses removed.
(valid_image_p): Use FOR_EACH_TAIL_SAFE to avoid Emacs hanging
if the user creates a circular description of an image.
(xbm_type, xpm_type, pbm_type, png_type, jpeg_type, tiff_type)
(gif_type, imagemagick_type, svg_type, gs_type):
Remove; now done by image_types.
(init_imagemagick_functions): Remove decl of nonexistent function.
(gs_clear_image): Remove; all uses replaced by image_clear_image.
(initialize_image_type): New function, which captures a lot
of the previously-scattered WINDOWSNT ifdefs.
(lookup_image_type): Use it.
(reset_image_types): Remove.  All uses removed.
(syms_of_image): Don’t worry about ignoring image_types for
pdumper, since it’s a constant now.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/dispextern.h b/src/dispextern.h
index 619f4c07675..e86ea6a02ae 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -3036,7 +3036,7 @@ struct image
   int hmargin, vmargin;
 
   /* Reference to the type of the image.  */
-  struct image_type *type;
+  struct image_type const *type;
 
   /* True means that loading the image failed.  Don't try again.  */
   bool load_failed_p;