Make TreeItem.getExpanded consistent across platforms #2834

When the children of a previously expanded TreeItem are removed, the
call to getExpanded() should continue to return "true". On Linux and
MacOS, this property is not persisted in the native widget and may
wrongfully return "false".

Author: ptziegler

tests/org.eclipse.swt.tests/JUnit Tests/org/eclipse/swt/tests/junit/Test_org_eclipse_swt_widgets_TreeItem.java

@@ -555,6 +555,8 @@ public void test_getExpanded() {
 	new TreeItem(treeItem, 0);
 	treeItem.setExpanded(true);
 	assertTrue(treeItem.getExpanded());
+	treeItem.removeAll();
+	assertTrue(treeItem.getExpanded());
 	treeItem.setExpanded(false);
 	assertFalse(treeItem.getExpanded());
 }