I recall it complained on mpfr-3.1.2 anyhow; the answer to the question is another question though:
* Why is the patch there in the first place? Pardon me if it's something too obvious, I just don't know.

In fact, the reason I left it commented was to trigger this discussion; I think it would be good practice 
overall, to reference the URLs of discussions about patches, to understand if they are relevant in a given context.
(there is a lot to learn and improve, by following this practice)