bug#51451: image-transform-original has a misleading name

[Juri Linkov]

>> image-transform-* commands are modifying the values of
>> image-transform-* variables.
>> Would you propose to rename variables as well?
>
> I didn't think about that, as the commands are what the user will see.
> Maybe we should.  Do you think it would be a good idea?

At least, currently there is consistency in naming of
image-transform-* functions and variables.  Whether
selecting such a prefix was a good choice is another question.

But if you see a problem only in the name of image-transform-original,
then it could be renamed to image-transform-set-original or maybe
better to image-transform-reset-to-original, i.e. to something more
descriptive, while keeping the existing name prefix.

PS: renaming to image-transform-reset-to-original will also require
renaming image-transform-reset to image-transform-reset-to-initial.