INT_ADD_WRAPV and friends considered harmful

[Eli Zaretskii]

Please take a look at the problem described in this bug report:

  https://debbugs.gnu.org/cgi/bugreport.cgi?bug=37006

The upshot is that an innocent use of INT_ADD_WRAPV, even by
experienced programmers, can quite unexpectedly produce spectacular
failures.  Frankly, I was astonished to discover this failure mode,
especially as it isn't clearly documented in the comments in
intprops.h.

AFAIU, INT_ADD_WRAPV and its ilk are safety devices: they prevent code
from failing in subtle and rare situations.  And safety devices cannot
themselves be unsafe, because that would contradict the raison d'être
of their very existence.

So I urge the Gnulib developers to please fix this deficiency, and
make these macros safe in such simple use cases.

TIA