Merge pull request #1004 from Dry-Leaf/bsd_build_fix

Added member to Logger struct expected by tun_bsd.go

src/core/core.go

@@ -210,4 +210,5 @@ type Logger interface {
 	Errorln(...interface{})
 	Debugf(string, ...interface{})
 	Debugln(...interface{})
+	Traceln(...interface{})
 }