Add list_for_each_entry_safe.

src/include/gpxe/list.h

  * @v member	The name of the list_struct within the struct
  */
 #define list_for_each_entry( pos, head, member )			      \
-	for ( pos = list_entry ( (head)->next, typeof ( *pos ), member);      \
+	for ( pos = list_entry ( (head)->next, typeof ( *pos ), member );     \
 	      &pos->member != (head);					      \
 	      pos = list_entry ( pos->member.next, typeof ( *pos ), member ) )
 
+/**
+ * Iterate over entries in a list, safe against deletion of entries
+ *
+ * @v pos	The type * to use as a loop counter
+ * @v tmp	Another type * to use for temporary storage
+ * @v head	The head for your list
+ * @v member	The name of the list_struct within the struct
+ */
+#define list_for_each_entry_safe( pos, tmp, head, member )		      \
+	for ( pos = list_entry ( (head)->next, typeof ( *pos ), member ),     \
+	      tmp = list_entry ( pos->member.next, typeof ( *tmp ), member ); \
+	      &pos->member != (head);					      \
+	      pos = tmp,						      \
+	      tmp = list_entry ( tmp->member.next, typeof ( *tmp ), member ) )
+
 #endif /* _GPXE_LIST_H */