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/ns.rde b/result/ns.rde
new file mode 100644
index 0000000..513d135
--- /dev/null
+++ b/result/ns.rde
@@ -0,0 +1,7 @@
+0 1 dia:diagram 0 0
+1 14 #text 0 1 
+  
+1 1 dia:diagramdata 1 0
+1 14 #text 0 1 
+
+0 15 dia:diagram 0 0