bug#35421: Also bind left image rotation key

[積丹尼 Dan Jacobson]

When viewing an image we type C-h m

   Image[imagemagick] mode defined in ‘image-mode.el’:

there is only one rotate command bound

   r            image-rotate

and it only rotates right. To rotate left one must hit it three times.

Also if we could see the whole image before rotation, its bottom is now
cut off after rotation. (landscape->portrait).