util: added a reverse insert (sorted) routine to TAILQ

This changes the way in which equal objects are handled. Previously they'd
be added to the HEAD and with this they add to the TAIL, which is what I
need in network scanning code.

src/queue.h

@@ -129,6 +129,24 @@
         }							\
 } while(0)
 
+#define TAILQ_INSERT_SORTED_R(head, headname, elm, field, cmpfunc) do { \
+        if(TAILQ_FIRST(head) == NULL) {				\
+           TAILQ_INSERT_HEAD(head, elm, field);			\
+        } else {						\
+           typeof(elm) _tmp;					\
+           TAILQ_FOREACH_REVERSE(_tmp,head,headname,field) {			\
+              if(cmpfunc(elm,_tmp) >= 0) {			\
+                TAILQ_INSERT_AFTER(head,_tmp,elm,field);		\
+                break;						\
+              }							\
+              if(!TAILQ_PREV(_tmp,headname,field)) {			\
+                 TAILQ_INSERT_BEFORE(_tmp,elm,field);	\
+                 break;						\
+              }							\
+           }							\
+        }							\
+} while(0)
+
 #define TAILQ_MOVE(newhead, oldhead, field) do { \
         if(TAILQ_FIRST(oldhead)) { \
            TAILQ_FIRST(oldhead)->field.tqe_prev = &(newhead)->tqh_first;  \