[modules] Introduce new VariableLocation for module imports/exports.

src/full-codegen/s390/full-codegen-s390.cc

Index: src/full-codegen/s390/full-codegen-s390.cc
diff --git a/src/full-codegen/s390/full-codegen-s390.cc b/src/full-codegen/s390/full-codegen-s390.cc
index 4bced1439da84a5a8de2fc3c93a80055f8264c67..44ef8c82294f1f0af7ab8e1cfc3b91acca019675 100644
--- a/src/full-codegen/s390/full-codegen-s390.cc
+++ b/src/full-codegen/s390/full-codegen-s390.cc
@@ -746,6 +746,9 @@ void FullCodeGenerator::VisitVariableDeclaration(
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -799,6 +802,9 @@ void FullCodeGenerator::VisitFunctionDeclaration(
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -1283,7 +1289,11 @@ void FullCodeGenerator::EmitVariableLoad(VariableProxy* proxy,
       __ CallRuntime(function_id);
       __ bind(&done);
       context()->Plug(r2);
+      break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }