Fix clang-tidy warnings in aapt and aapt2.

* Add explicit keyword to conversion constructors.
* Add NOLINT(implicit) comments for implicit conversion constructors.
Bug: 28341362
* Use const reference type for read-only parameters.
Bug: 30407689
* Add NOLINT to suppress wrong clang-tidy warnings on macros.
Test: build with WITH_TIDY=1

Change-Id: Ibfafb23d9be463b4072745a51a6d9f1812dcac45
diff --git a/tools/aapt2/xml/XmlPullParser.h b/tools/aapt2/xml/XmlPullParser.h
index ee51b36..a24d109 100644
--- a/tools/aapt2/xml/XmlPullParser.h
+++ b/tools/aapt2/xml/XmlPullParser.h
@@ -60,7 +60,7 @@
     static bool skipCurrentElement(XmlPullParser* parser);
     static bool isGoodEvent(Event event);
 
-    XmlPullParser(std::istream& in);
+    explicit XmlPullParser(std::istream& in);
     ~XmlPullParser();
 
     /**