bug#35421: Also bind left image rotation key

[Basil L. Contovounesios]

積丹尼 Dan Jacobson <jidanni@jidanni.org> writes:

> args
> 1,2,3=
> 90,180,270
> or something like that.

Image viewers like gThumb provide buttons for rotations in steps of 90
degrees, and Emacs isn't even an image viewer, so there's no need to
complicate and restrict (w.r.t. future changes) the command's calling
convention like that.

Instead, the proposed patch[1] makes the simplest possible change to
support counter-clockwise rotations in one step, rather than three.  In
addition, it makes image-rotate accept arbitrary rotation angles when
called from Lisp, so you can use it to easily write your own
image-rotating command, with your preferred calling convention.

[1]: https://debbugs.gnu.org/35421#31

-- 
Basil