adding namespace checkings while making sure they still parse as

* parser.c parserInternals.c tree.c include/libxml/parser.h
  include/libxml/xmlerror.h: adding namespace checkings
  while making sure they still parse as wellformed documents.
  Add an nsWellFormed status report to the context, and
  provide new appropriate error codes.
* Makefile.am result/namespaces/* test/namespaces/*: add
  specific regression testing for the new namespace support
* test/att5 result/noent/att5 result/att5 result/att5.sax:
  add more coverage for the attribute parsing and normalization
  code.
Daniel
diff --git a/tree.c b/tree.c
index a68beb9..ba3cbf2 100644
--- a/tree.c
+++ b/tree.c
@@ -151,8 +151,8 @@
     int lenn, lenp;
     xmlChar *ret;
 
-    if ((ncname == NULL) || (*ncname == 0)) return(NULL);
-    if ((prefix == NULL) || (*prefix == 0)) return((xmlChar *) ncname);
+    if (ncname == NULL) return(NULL);
+    if (prefix == NULL) return((xmlChar *) ncname);
 
     lenn = strlen((char *) ncname);
     lenp = strlen((char *) prefix);