fixed a serious problem when substituing entities using the Reader, the

* parser.c xmlreader.c include/libxml/parser.h: fixed a serious
  problem when substituing entities using the Reader, the entities
  content might be freed and if rereferenced would crash
* Makefile.am test/* result/*: added a new test case and a new
  test operation for the reader with substitution of entities.
Daniel
diff --git a/result/dav6.rde b/result/dav6.rde
new file mode 100644
index 0000000..726e3c2
--- /dev/null
+++ b/result/dav6.rde
@@ -0,0 +1,63 @@
+0 1 D:multistatus 0 0
+1 14 #text 0 1 
+  
+1 1 D:response 0 0
+2 14 #text 0 1 
+    
+2 1 D:href 0 0
+3 3 #text 0 1 http://www.microsoft.com/user/yarong/dav_drafts/
+      
+2 15 D:href 0 0
+2 14 #text 0 1 
+    
+2 1 D:prop 0 0
+3 14 #text 0 1 
+      
+3 1 D:resourcetype 0 0
+4 14 #text 0 1 
+        
+4 1 D:collection 1 0
+4 14 #text 0 1 
+      
+3 15 D:resourcetype 0 0
+3 14 #text 0 1 
+    
+2 15 D:prop 0 0
+2 14 #text 0 1 
+    
+2 1 D:status 0 0
+3 3 #text 0 1 HTTP 1.1 200 OK
+2 15 D:status 0 0
+2 14 #text 0 1 
+  
+1 15 D:response 0 0
+1 14 #text 0 1 
+  
+1 1 D:response 0 0
+2 14 #text 0 1 
+    
+2 1 D:href 0 0
+3 3 #text 0 1 
+      http://www.microsoft.com/user/yarong/dav_drafts/base
+      
+2 15 D:href 0 0
+2 14 #text 0 1 
+    
+2 1 D:prop 0 0
+3 14 #text 0 1 
+      
+3 1 D:resourcetype 1 0
+3 14 #text 0 1 
+    
+2 15 D:prop 0 0
+2 14 #text 0 1 
+    
+2 1 D:status 0 0
+3 3 #text 0 1 HTTP 1.1 200 OK
+2 15 D:status 0 0
+2 14 #text 0 1 
+  
+1 15 D:response 0 0
+1 14 #text 0 1 
+
+0 15 D:multistatus 0 0