Fix a bunch of scan 'dead increments' and cleanup

* HTMLparser.c c14n.c debugXML.c entities.c nanohttp.c parser.c
  testC14N.c uri.c xmlcatalog.c xmllint.c xmlregexp.c xpath.c:
  fix unused variables, or unneeded increments as well as a couple
  of space issues
* runtest.c: check for NULL before calling unlink()
diff --git a/c14n.c b/c14n.c
index 5c6c456..9c3cad2 100644
--- a/c14n.c
+++ b/c14n.c
@@ -2226,7 +2226,7 @@
         }
         cur++;
     }
-    *out++ = 0;
+    *out = 0;
     return (buffer);
 }
 #endif /* LIBXML_OUTPUT_ENABLED */