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()

HTMLparser.c

@@ -2560,7 +2560,7 @@ htmlParseHTMLAttribute(htmlParserCtxtPtr ctxt, const xmlChar stop) {
 	    NEXT;
 	}
     }
-    *out++ = 0;
+    *out = 0;
     return(buffer);
 }