FieldDecl::getParent fires assert for Objective C @interface members

(like in vcl/inc/osx/a11ywrapper.h's AquaA11yWrapper), at least on recent Clang
trunk, from within the call to cast() in

  cast<RecordDecl>(getDeclContext())

as the decl context apparently is something other than a RecordDecl.

Change-Id: I238bae44d6db0f04bf8f90b0032489e3b4822eee

compilerplugins/clang/datamembershadow.cxx

@@ -96,7 +96,7 @@ bool DataMemberShadow::VisitFieldDecl(FieldDecl const * fieldDecl)
     if (aFileName == SRCDIR "/xmloff/source/draw/ximplink.hxx")
         return true;
 
-    const CXXRecordDecl* parentCXXRecordDecl = dyn_cast<CXXRecordDecl>(fieldDecl->getParent());
+    const CXXRecordDecl* parentCXXRecordDecl = dyn_cast<CXXRecordDecl>(fieldDecl->getDeclContext());
     if (!parentCXXRecordDecl) {
         return true;
     }