utf8: accept "latin-1" as ISO-8859-1

Even though latin-1 is still seen in e-mail headers, some platforms
only install ISO-8859-1.  "iconv -f ISO-8859-1" succeeds, while
"iconv -f latin-1" fails on such a system.

Using the same fallback_encoding() mechanism factored out in the
previous step, teach ourselves that "ISO-8859-1" has a better chance
of being accepted than "latin-1".

Signed-off-by: Junio C Hamano <gitster@pobox.com>

utf8.c

@@ -501,6 +501,13 @@ static const char *fallback_encoding(const char *name)
 	if (is_encoding_utf8(name))
 		return "UTF-8";
 
+	/*
+	 * Even though latin-1 is still seen in e-mail
+	 * headers, some platforms only install ISO-8859-1.
+	 */
+	if (!strcasecmp(name, "latin-1"))
+		return "ISO-8859-1";
+
 	return name;
 }