Add C++ header to AidlParcelable

In situations where a parcelable declaration includes a C++ header,
propagate that information to the AidlParcelable object.  While here:

 - remove support for the C++ type alias (the is keyword)
 - consolidate AidlParcelable constructors to always use
   AidlQualifiedName

Bug: 23600712
Test: unittests pass, integration tests pass

Change-Id: I058d8c2012bb0e5e07bbb6599ac5108f7866ad6e
diff --git a/aidl.cpp b/aidl.cpp
index 8e54211..6221846 100644
--- a/aidl.cpp
+++ b/aidl.cpp
@@ -438,7 +438,8 @@
     }
 
     if (decl == "parcelable") {
-      AidlParcelable doc(class_name, lineno, package);
+      AidlParcelable doc(new AidlQualifiedName(class_name, ""),
+                         lineno, package);
       types->AddParcelableType(&doc, filename);
     } else if (decl == "interface") {
       auto temp = new std::vector<std::unique_ptr<AidlMethod>>();