[mod_auth] send charset="UTF-8" in WWW-Authenticate (fixes #1468)

https://tools.ietf.org/html/rfc7616 and
https://tools.ietf.org/html/rfc7617 (September 2015)
update Digest and Basic auth to allow server to recommend charset
which should be used by client.

http://stackoverflow.com/questions/702629/utf-8-characters-mangled-in-http-basic-auth-username

x-ref:
  "LDAP UTF-8 encoding"
  https://redmine.lighttpd.net/issues/1468

NEWS

@@ -64,6 +64,7 @@ NEWS
   * [core] clean up srv before exiting for lighttpd -[vVh]
   * [mod_fastcgi,mod_scgi] check for spawning on same unix socket (fixes #319)
   * [mod_cgi] always set QUERY_STRING (fixes #1339)
+  * [mod_auth] send charset="UTF-8" in WWW-Authenticate (fixes #1468)
 
 - 1.4.39 - 2016-01-02
   * [core] fix memset_s call (fixes #2698)

src/mod_auth.c

@@ -298,7 +298,7 @@ static handler_t mod_auth_uri_handler(server *srv, connection *con, void *p_d) {
 		if (0 == strcmp(method->value->ptr, "basic")) {
 			buffer_copy_string_len(p->tmp_buf, CONST_STR_LEN("Basic realm=\""));
 			buffer_append_string_buffer(p->tmp_buf, realm->value);
-			buffer_append_string_len(p->tmp_buf, CONST_STR_LEN("\""));
+			buffer_append_string_len(p->tmp_buf, CONST_STR_LEN("\", charset=\"UTF-8\""));
 
 			response_header_insert(srv, con, CONST_STR_LEN("WWW-Authenticate"), CONST_BUF_LEN(p->tmp_buf));
 		} else if (0 == strcmp(method->value->ptr, "digest")) {
@@ -307,7 +307,7 @@ static handler_t mod_auth_uri_handler(server *srv, connection *con, void *p_d) {
 
 			buffer_copy_string_len(p->tmp_buf, CONST_STR_LEN("Digest realm=\""));
 			buffer_append_string_buffer(p->tmp_buf, realm->value);
-			buffer_append_string_len(p->tmp_buf, CONST_STR_LEN("\", nonce=\""));
+			buffer_append_string_len(p->tmp_buf, CONST_STR_LEN("\", charset=\"UTF-8\", nonce=\""));
 			buffer_append_string(p->tmp_buf, hh);
 			buffer_append_string_len(p->tmp_buf, CONST_STR_LEN("\", qop=\"auth\""));