Correctly widen bounds for exprs not containing addition or multiplication

[mgrang]

Handle the following case in bounds widening:

void f(int i) {
  _Nt_array_ptr<char> p : bounds(p, p - i + 0) = "a";

  if (*(p - i))
  {}
}

We call the function NormalizeExprsWithoutConst which adds 0 constant to expressions not containing an integer constant. But the problem is we only add + 0 to an expression which contains addition and * 1 to an expression which contains multiplication. In the above case, we do not have addition or multiplication in the deref expression. This results in the bounds not getting widened.

The proper fix for this is to always add + 0 to every expression without checking the operator. This 0 constant would anyway be constant folded. So it should not be a problem.

[mgrang]

Fixed in #944