[Interpreter] Add support for calling runtime functions which return a pair.

src/compiler/linkage.h

Index: src/compiler/linkage.h
diff --git a/src/compiler/linkage.h b/src/compiler/linkage.h
index d75a3e7ea6478425e0449a865fbf9b95d6779fe5..252f0443213e522875697d8013649d58a02977a0 100644
--- a/src/compiler/linkage.h
+++ b/src/compiler/linkage.h
@@ -319,7 +319,8 @@ class Linkage : public ZoneObject {
       Isolate* isolate, Zone* zone, const CallInterfaceDescriptor& descriptor,
       int stack_parameter_count, CallDescriptor::Flags flags,
       Operator::Properties properties = Operator::kNoProperties,
-      MachineType return_type = MachineType::AnyTagged());
+      MachineType return_type = MachineType::AnyTagged(),
+      size_t return_count = 1);
 
   // Creates a call descriptor for simplified C calls that is appropriate
   // for the host platform. This simplified calling convention only supports