do not infloop on a query ending in %XY, for invalid hex X or Y

When a query ends in say %gg, (or any invalid hex) e.g.,
http://git.gnome.org/browse/gdlmm/commit/?id=%gg
convert_query_hexchar calls memmove(txt, txt+3, 0), and then returns
txt-1, so the loop in http_parse_querystring never terminates.  The
solution is to make the memmove also copy the trailing NUL.
* html.c (convert_query_hexchar): Fix off-by-one error.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

html.c

@@ -249,7 +249,7 @@ char *convert_query_hexchar(char *txt)
 	d1 = hextoint(*(txt+1));
 	d2 = hextoint(*(txt+2));
 	if (d1<0 || d2<0) {
-		memmove(txt, txt+3, n-3);
+		memmove(txt, txt+3, n-2);
 		return txt-1;
 	} else {
 		*txt = d1 * 16 + d2;