Adjust documentation for new.instance() to reflect that the second

parameter may be omitted or None.

Doc/lib/libnew.tex

@@ -14,10 +14,12 @@ to the interpreter, so care must be exercised when using this module.
 
 The \module{new} module defines the following functions:
 
-\begin{funcdesc}{instance}{class, dict}
+\begin{funcdesc}{instance}{class\optional{, dict}}
 This function creates an instance of \var{class} with dictionary
-\var{dict} without calling the \method{__init__()} constructor. Note that
-there are no guarantees that the object will be in a consistent state.
+\var{dict} without calling the \method{__init__()} constructor.  If
+\var{dict} is omitted or \code{None}, a new, empty dictionary is
+created for the new instance.  Note that there are no guarantees that
+the object will be in a consistent state.
 \end{funcdesc}
 
 \begin{funcdesc}{instancemethod}{function, instance, class}