Changed xmlSchemaFormatIDCKeySequence() to use

* xmlschemas.c: Changed xmlSchemaFormatIDCKeySequence()
  to use xmlSchemaGetCanonValueWhtspExt() in order to
  correctly report values for xs:anySimpleType.
* test/schemas/idc-keyref-err1*
  result/schemas/idc-keyref-err1*: Added a test for this change.

test/schemas/idc-keyref-err1_0.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0"?>
+<Foo
+	xmlns="urn:test:foo"
+	xmlns:foo="urn:test:foo"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="urn:test:foo idc-keyref_1.xsd">
+
+    <Def>
+        <Link foo:linkKey="L4"/>
+    </Def>
+
+    <Ref foo:linkRef="L4"/>
+
+</Foo> 

test/schemas/idc-keyref-err1_1.xsd

@@ -0,0 +1,53 @@
+<?xml version="1.0"?>
+<xs:schema
+    targetNamespace="urn:test:foo"
+    xmlns:xs="http://www.w3.org/2001/XMLSchema"
+    xmlns:foo="urn:test:foo"
+    elementFormDefault="qualified"
+    attributeFormDefault="qualified">
+  
+   <xs:element name="Link">
+       <xs:complexType>
+           <xs:simpleContent>
+               <xs:extension base="xs:string">
+                   <xs:attribute name="linkKey" type="xs:string" use="required"/>
+               </xs:extension>
+           </xs:simpleContent>
+       </xs:complexType>
+   </xs:element>
+      
+    
+  <!--  -->
+  <xs:element name="Foo">
+    <xs:complexType>
+      <xs:sequence>
+	          
+        <xs:element name="Def">
+            <xs:complexType>
+                <xs:sequence>
+                    <xs:element ref="foo:Link"/>
+                </xs:sequence>
+            </xs:complexType>
+        </xs:element>
+        
+        <xs:element name="Ref">
+            <xs:complexType>
+                <xs:attribute name="linkRef" use="required"/>
+            </xs:complexType>
+        </xs:element>
+
+      </xs:sequence>
+	</xs:complexType>      
+
+	<xs:key name="LinkKey">
+	  <xs:selector xpath=".//foo:Link | .//foo:Link"/>
+	  <xs:field xpath="@foo:linkKey"/>
+	</xs:key>
+
+	<xs:keyref name="LinkKeyRef" refer="foo:LinkKey">
+	  <xs:selector xpath=".//foo:Ref"/>
+	  <xs:field xpath="@foo:linkRef"/>
+	</xs:keyref>    
+  </xs:element>
+
+</xs:schema>