reencode_string: use size_t for string lengths

The iconv interface takes a size_t, which is the appropriate
type for an in-memory buffer. But our reencode_string_*
functions use integers, meaning we may get confusing results
when the sizes exceed INT_MAX. Let's use size_t
consistently.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

strbuf.c

@@ -134,7 +134,7 @@ void strbuf_ltrim(struct strbuf *sb)
 int strbuf_reencode(struct strbuf *sb, const char *from, const char *to)
 {
 	char *out;
-	int len;
+	size_t len;
 
 	if (same_encoding(from, to))
 		return 0;