Fix google-explicit-constructor warnings in system/core.

* Declare explicit conversion constructors.
* Add NOLINT for implicit conversion constructors.
* Fix also some misaligned indendations.

Bug: 28341362
Change-Id: Idf911f35923b408d92285cc1a053f382ba08c63e
Test: build with clang-tidy
diff --git a/logd/LogReader.h b/logd/LogReader.h
index 98674b8..fdcedf1 100644
--- a/logd/LogReader.h
+++ b/logd/LogReader.h
@@ -27,7 +27,7 @@
     LogBuffer &mLogbuf;
 
 public:
-    LogReader(LogBuffer *logbuf);
+    explicit LogReader(LogBuffer *logbuf);
     void notifyNewLog();
 
     LogBuffer &logbuf(void) const { return mLogbuf; }