Bug #1597576: mention that the new base64 api has been introduced in py2.4.
diff --git a/Doc/lib/libbase64.tex b/Doc/lib/libbase64.tex
index 0039c84..d7eccbd 100644
--- a/Doc/lib/libbase64.tex
+++ b/Doc/lib/libbase64.tex
@@ -21,7 +21,7 @@
decoding to and from file-like objects as well as strings, but only
using the Base64 standard alphabet.
-The modern interface provides:
+The modern interface, which was introduced in Python 2.4, provides:
\begin{funcdesc}{b64encode}{s\optional{, altchars}}
Encode a string use Base64.