Bugfix: Need signed types for ntime min/max offsets

Conflicts:
	miner.h

miner.h

@@ -1198,8 +1198,8 @@ struct bfg_tmpl_ref {
 struct ntime_roll_limits {
 	uint32_t min;
 	uint32_t max;
-	uint16_t minoff;
-	uint16_t maxoff;
+	int16_t minoff;
+	int16_t maxoff;
 };
 
 struct stratum_work {