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
6 files changed