system/core: preparation to pull back interfaces from android/log.h

Point to log/log.h where necessary, define LOG_TAG where necessary.
Accept that private/android_logger.h is suitable replacement for
log/logger.h and android/log.h.

Correct liblog/README

Effectively a cleanup and controlled select revert of
'system/core: drop or replace log/logger.h' and
'system/core: Replace log/log.h with android/log.h'.

Test: compile
Bug: 30465923
Change-Id: Ic2ad157bad6f5efe2c6af293a73bb753300b17a2

lmkd.c

@@ -18,6 +18,7 @@
 
 #include <arpa/inet.h>
 #include <errno.h>
+#include <sched.h>
 #include <signal.h>
 #include <stdlib.h>
 #include <string.h>