bug#69602: 29.1; Image :map should adjust with :scale and :rotation

[Eli Zaretskii]

> From: Joseph Turner <joseph@breatheoutbreathe.in>
> Date: Thu, 07 Mar 2024 23:02:24 -0800
> 
> Joseph Turner <joseph@breatheoutbreathe.in> writes:
> 
> > The attached patch adds two hooks in `image.el' which allow packages to
> > recompute an image's map after it's rescaled or rotated.
> 
> In this new attached patch, rescaling image maps is handled within
> image.el.  No new hooks are added.  This change should be backwards
> compatible, except that :unscaled-map is now a reserved image property.

Are we sure no Lisp program out there would want the coordinates in
:map to remain unchanged under these transformation?  Maybe we should
add a variable to control this, so that the change could be truly
backward-compatible?

> If we decide to install this patch, I'll work on modifying image maps
> inside of `image-rotate', as well as update the manual and NEWS.

Thanks.