(libformatter.tex): Document the flush() method on the writer.

Doc/lib/libformatter.tex

@@ -216,6 +216,10 @@ application.
 
 \renewcommand{\indexsubitem}{(writer object method)}
 
+\begin{funcdesc}{flush}{}
+Flush any buffered output or device control events.
+\end{funcdesc}
+
 \begin{funcdesc}{new_alignment}{align}
 Set the alignment style.  The \code{align} value can be any object,
 but by convention is a string or \code{None}, where \code{None}

Doc/libformatter.tex

@@ -216,6 +216,10 @@ application.
 
 \renewcommand{\indexsubitem}{(writer object method)}
 
+\begin{funcdesc}{flush}{}
+Flush any buffered output or device control events.
+\end{funcdesc}
+
 \begin{funcdesc}{new_alignment}{align}
 Set the alignment style.  The \code{align} value can be any object,
 but by convention is a string or \code{None}, where \code{None}