a lot of small cleanups based on Linus' sparse check output. Daniel

* HTMLparser.c SAX2.c encoding.c globals.c parser.c relaxng.c
  runsuite.c runtest.c schematron.c testHTML.c testReader.c
  testRegexp.c testSAX.c testThreads.c valid.c xinclude.c xmlIO.c
  xmllint.c xmlmodule.c xmlschemas.c xpath.c xpointer.c: a lot of
  small cleanups based on Linus' sparse check output.
Daniel
diff --git a/encoding.c b/encoding.c
index 66e63b5..3f5d8b4 100644
--- a/encoding.c
+++ b/encoding.c
@@ -1239,7 +1239,7 @@
     const char *alias;
     char upper[500];
     int i;
-    char *up = 0;
+    char *up = NULL;
 
     /*
      * Do the alias resolution