message: [SwiftASTContext] Register the request functions when creating a context.
  Not doing that results in the state not properly set up, and an
  assertion hit in the compiler. No test as several are already failing
  on the bots, so we have coverage.
  <rdar://problem/41738966>
diff: @@ -2911,6 +2911,9 @@ swift::ASTContext *SwiftASTContext::GetASTContext() {
  m_ast_context_ap->addModuleLoader(std::move(serialized_module_loader_ap));
  }
  + // Set up the required state for the evaluator in the TypeChecker.
  + registerTypeCheckerRequestFunctions(m_ast_context_ap->evaluator);
  +
  GetASTMap().Insert(m_ast_context_ap.get(), this);
  }
  