Make sure we include all of Python's numeric types in the data model

description, so that the introduction of complex is not a surprise.

This closes SF bug #423429.

Doc/ref/ref3.tex

@@ -159,7 +159,8 @@ numbers are of course strongly related to mathematical numbers, but
 subject to the limitations of numerical representation in computers.
 \obindex{numeric}
 
-Python distinguishes between integers and floating point numbers:
+Python distinguishes between integers, floating point numbers, and
+complex numbers:
 
 \begin{description}
 \item[Integers]