Please implement http://gcc.gnu.org/ml/gcc-patches/2006-06/msg01047.html

This is useful because previously, gcc-4.0.1 didn't warn about this case:

void f(void *last, ...) __attribute__((sentinel(0,1)));

main() {
  f((void*)0);
}

but gcc-4.2 does.  We have APIs that make use of the null being in the first argument and they used the sentinel check, but now clients get lots of warnings due to the `new' behavior.

We've added this to our compiler, just 49 lines...

radr://5631180