[modules] If we add an implicit special member to a class through an update

record, and that class declaration is not the canonical definition of the
class, be sure to add the class to the list of classes that are consulted when
we look up a special member in the canonical definition.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@226778 91177308-0d34-0410-b5e6-96231b3b80d8