logd: make liblogd just the core logd functionality

liblogd: LogBuffer classes and their support, LogReaderList and
LogReaderThread
logd: liblogd + the socket code that connects liblogd to liblog and
therefore the world.

The goal here is to test liblogd offline of the socket connections or
the device.

Also, convert libaudit.c -> libaudit.cpp and modernize a bit.

Test: build
Change-Id: If5adf5e775a251d9a703c0583be0988f48017347
diff --git a/logd/libaudit.h b/logd/libaudit.h
index b4a92a8..27b0866 100644
--- a/logd/libaudit.h
+++ b/logd/libaudit.h
@@ -17,8 +17,7 @@
  * Written by William Roberts <w.roberts@sta.samsung.com>
  */
 
-#ifndef _LIBAUDIT_H_
-#define _LIBAUDIT_H_
+#pragma once
 
 #include <stdint.h>
 #include <sys/cdefs.h>
@@ -102,5 +101,3 @@
 extern int audit_rate_limit(int fd, uint32_t limit);
 
 __END_DECLS
-
-#endif