Discouraged access: The type InternalXSDMultiPageEditor is not accessible due to restriction on required library [...]\org.eclipse.wst.xsd.ui_1.2.500.v201203081826.jar
<editor class="org.eclipse.wst.xsd.ui.internal.editor.InternalXSDMultiPageEditor" extensions="xsd" id="com.foo.MyXSDEditorID" [...] </editor>