Added buffer_info() docs.

Doc/lib/libarray.tex

@@ -60,6 +60,16 @@ The length in bytes of one array item in the internal representation.
 Append a new item with value \var{x} to the end of the array.
 \end{funcdesc}
 
+\begin{funcdesc}{buffer_info}{}
+Return a tuple \code{(\var{address}, var{length})} giving the current
+memory address and the length in bytes of the buffer used to hold
+array's contents.  This is occasionally useful when working with
+low-level (and inherently unsafe) I/O interfaces that require memory
+addresses, such as certain \code{ioctl} operations.  The returned
+numbers are valid as long as the array exists and no length-changing
+operations are applied to it.
+\end{funcdesc}
+
 \begin{funcdesc}{byteswap}{x}
 ``Byteswap'' all items of the array.  This is only supported for
 integer values.  It is useful when reading data from a file written

Doc/libarray.tex

@@ -60,6 +60,16 @@ The length in bytes of one array item in the internal representation.
 Append a new item with value \var{x} to the end of the array.
 \end{funcdesc}
 
+\begin{funcdesc}{buffer_info}{}
+Return a tuple \code{(\var{address}, var{length})} giving the current
+memory address and the length in bytes of the buffer used to hold
+array's contents.  This is occasionally useful when working with
+low-level (and inherently unsafe) I/O interfaces that require memory
+addresses, such as certain \code{ioctl} operations.  The returned
+numbers are valid as long as the array exists and no length-changing
+operations are applied to it.
+\end{funcdesc}
+
 \begin{funcdesc}{byteswap}{x}
 ``Byteswap'' all items of the array.  This is only supported for
 integer values.  It is useful when reading data from a file written