Provide a copy_work_noffset function for copying a work struct but changing its ntime.

cgminer.c

@@ -3618,12 +3618,14 @@ static void _copy_work(struct work *work, const struct work *base_work, int noff
 }
 
 /* Generates a copy of an existing work struct, creating fresh heap allocations
- * for all dynamically allocated arrays within the struct */
+ * for all dynamically allocated arrays within the struct. noffset is used for
-struct work *copy_work(struct work *base_work)
+ * when a driver has internally rolled the ntime, noffset is a relative value.
+ * The macro copy_work() calls this function with an noffset of 0. */
+struct work *copy_work_noffset(struct work *base_work, int noffset)
 {
 	struct work *work = make_work();
 
-	_copy_work(work, base_work, 0);
+	_copy_work(work, base_work, noffset);
 
 	return work;
 }

miner.h

@@ -1532,7 +1532,8 @@ extern void adl(void);
 extern void app_restart(void);
 extern void clean_work(struct work *work);
 extern void free_work(struct work *work);
-extern struct work *copy_work(struct work *base_work);
+extern struct work *copy_work_noffset(struct work *base_work, int noffset);
+#define copy_work(work_in) copy_work_noffset(work_in, 0)
 extern struct thr_info *get_thread(int thr_id);
 extern struct cgpu_info *get_devices(int id);