Recognize global variables as array bounds

[john-h-kastner]

This is a pattern I've noticed 3c bounds inference doesn't support while converting yacr2

extern int baz;
void foo(int *a) {
  for (int i = 0; i < baz; i++) {
    (void) a[i];
  }
}

Here baz is being used as the length of a, so I would like to get _Array_ptr<int> a : count(baz). This is the result we see if baz is instead a parameter of foo.

[kyleheadley]

From a conversion perspective, I agree. I wonder if, from a safety perspective, we should issue an error, or go so far as to rewrite calls to foo with baz as a second parameter.

[Machiry]

We do use this heuristic for the same scope variables i.e., pointer and the bounds are in the same scope. But sure, we could do it.

[Machiry]

Fixed.