Use setVisible instead of re-parenting for RAP

Re-parenting is not yet supported by RAP. Use setVisible to hide
invisible parts instead of moving them to the "limbo" shell.
diff --git a/bundles/org.eclipse.e4.ui.workbench.swt/src/org/eclipse/e4/ui/internal/workbench/swt/PartRenderingEngine.java b/bundles/org.eclipse.e4.ui.workbench.swt/src/org/eclipse/e4/ui/internal/workbench/swt/PartRenderingEngine.java
index 5ff41a6..5c23962 100644
--- a/bundles/org.eclipse.e4.ui.workbench.swt/src/org/eclipse/e4/ui/internal/workbench/swt/PartRenderingEngine.java
+++ b/bundles/org.eclipse.e4.ui.workbench.swt/src/org/eclipse/e4/ui/internal/workbench/swt/PartRenderingEngine.java
@@ -173,7 +173,9 @@
 						Composite realComp = (Composite) renderer
 								.getUIContainer(changedElement);
 						Control ctrl = (Control) changedElement.getWidget();
-						ctrl.setParent(realComp);
+// RAP: re-parenting not supported
+//						ctrl.setParent(realComp);
+						ctrl.setVisible(true);
 						fixZOrder(changedElement);
 					}
 
@@ -193,7 +195,9 @@
 								SWT.DEFER);
 					}
 
-					ctrl.setParent(getLimboShell());
+// RAP: re-parenting not supported
+//					ctrl.setParent(getLimboShell());
+					ctrl.setVisible(false);
 				}
 
 				if (parent instanceof MElementContainer<?>) {