logd: klogd deal with nuls in dmesg

Switch to using string and length in all transactions, treating
trailing nuls the same as spaces.

ToDo: change dumpstate (bugreport) to use logcat -b printable _regardless_

Bug: 23517551
Change-Id: I42162365e6bf8ed79d356e7b689a673902116fdb
diff --git a/logd/LogAudit.h b/logd/LogAudit.h
index f977be9..2342822 100644
--- a/logd/LogAudit.h
+++ b/logd/LogAudit.h
@@ -28,7 +28,7 @@
 
 public:
     LogAudit(LogBuffer *buf, LogReader *reader, int fdDmesg);
-    int log(char *buf);
+    int log(char *buf, size_t len);
 
 protected:
     virtual bool onDataAvailable(SocketClient *cli);