Thanks, I pushed that with minor changes to the ChangeLog message (first 
attached patch).  It's a tad faster to combine the relevant flags at 
compile-time so I did that (second attached patch).

"Iff" means "if and only if"; see <http://en.wikipedia.org/wiki/Iff>.  I
got the habit of trying to be logically-precise from RMS, who I guess
got it back in the days when he was doing AI.  Anyway, I reworded the 
text in a different way to avoid the misuse of "if" (third attached patch).