Add a note about "as" not being a keyword, though it has special meaning

when used as part of the import statement.

Note that both "as" and "None" becoming keywords in the future.

Closes SF bug #553262.

Doc/ref/ref2.tex

@@ -272,6 +272,13 @@ def       finally   in        print
 
 % When adding keywords, use reswords.py for reformatting
 
+Note that although the identifier \code{as} can be used as part of the
+syntax of \keyword{import} statements, it is not currently a reserved
+word.
+
+In some future version of Python, the identifiers \code{as} and
+\code{None} will both become keywords.
+
 
 \subsection{Reserved classes of identifiers\label{id-classes}}