glsl: Add typed foreach_in_list_safe macro.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

src/glsl/list.h

@@ -583,6 +583,15 @@ inline void exec_node::insert_before(exec_list *before)
         !(__inst)->is_head_sentinel();                  \
         (__inst) = (__type *)(__inst)->prev)
 
+/**
+ * This version is safe even if the current node is removed.
+ */ 
+#define foreach_in_list_safe(__type, __node, __list) \
+   for (__type *__node = (__type *)(__list)->head,   \
+               *__next = (__type *)__node->next;     \
+        __next != NULL;                              \
+        __node = __next, __next = (__type *)__next->next)
+
 /**
  * Iterate through two lists at once.  Stops at the end of the shorter list.
  *