[Bug c++/114571] -Wzero-as-null-pointer-constant does not complain about NULL

[ossman at cendio dot se via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114571

--- Comment #2 from Pierre Ossman <ossman at cendio dot se> ---
Found another case that neither gcc 5, gcc 13, nor clang complain about for
some odd reason:

>  assert(thing == NULL);

All three complain about:

>  assert(thing == 0);

Not sure what's going on here.