small patch from Philip Ludlam to avoid warnings. Daniel

* xpath.c: small patch from Philip Ludlam to avoid warnings.
Daniel
diff --git a/xpath.c b/xpath.c
index 9bf5571..0986986 100644
--- a/xpath.c
+++ b/xpath.c
@@ -562,13 +562,13 @@
         ((op == XPATH_OP_FUNCTION) || (op == XPATH_OP_VARIABLE) ||
 	 (op == XPATH_OP_COLLECT))) {
         if (value4 != NULL) {
-	    comp->steps[comp->nbStep].value4 = 
+	    comp->steps[comp->nbStep].value4 = (xmlChar *)
 	        (void *)xmlDictLookup(comp->dict, value4, -1);
 	    xmlFree(value4);
 	} else
 	    comp->steps[comp->nbStep].value4 = NULL;
         if (value5 != NULL) {
-	    comp->steps[comp->nbStep].value5 = 
+	    comp->steps[comp->nbStep].value5 = (xmlChar *)
 	        (void *)xmlDictLookup(comp->dict, value5, -1);
 	    xmlFree(value5);
 	} else