Use DBUG_ASSERT(ptr != NULL) to ease merging to 10.3

In 10.3, DBUG_ASSERT() may expand to something that includes __builtin_expect(), which expects integer arguments, not pointers. To avoid any compiler warnings, let us use an explicit rather than implicit comparison to the null pointer.

Author: dr-m

include/ilist.h

@@ -71,12 +71,12 @@ template <class T, class Tag= void> class ilist
  typedef T *pointer;
  typedef T &reference;
 
- Iterator(ListNode *node) : node_(node) { DBUG_ASSERT(node_); }
+ Iterator(ListNode *node) : node_(node) { DBUG_ASSERT(node_ != NULL); }
 
  Iterator &operator++()
  {
  node_= node_->next;
- DBUG_ASSERT(node_);
+ DBUG_ASSERT(node_ != NULL);
  return *this;
  }
  Iterator operator++(int)