Mention FutureWarning for large ints

Doc/whatsnew/whatsnew23.tex

@@ -2073,6 +2073,11 @@ objects are converted to their Python equivalent, if one exists, or
 wrapped with a \class{_tkinter.Tcl_Obj} object if no Python equivalent
 exists.
 
+\item Large octal and hex literals such as
+0xffffffff now trigger a \exception{FutureWarning} because currently
+they're stored as 32-bit numbers and result in a negative value, but
+in Python 2.4 they'll become positive long integers.  
+
 \item You can no longer disable assertions by assigning to \code{__debug__}.
 
 \item The Distutils \function{setup()} function has gained various new