** Code that uses `concat' with integer args now gets an error, as
long promised.
+** The function base64-decode-string now always returns a unibyte
+string.
+
** Not a Lisp incompatibility as such but, with the introduction of
extra private charsets, there is now only one slot free for a new
dimension-2 private charset. User code which tries to add more than
argument function's results.
** The functions base64-decode-region and base64-decode-string now
-signal an error instead of returning nil if decoding fails.
+signal an error instead of returning nil if decoding fails. Also,
+base64-decode-string now always returns a unibyte string (in Emacs 20,
+it returned a multibyte string when the result was a valid multibyte
+sequence).
** The function sendmail-user-agent-compose now recognizes a `body'
header in the list of headers passed to it.