Added lost docs for crypt module.

Doc/libcrypt.tex

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+\section{Built-in module {\tt crypt}}
+\bimodindex{crypt}
+
+This module implements an interface to the crypt({\bf 3}) routine,
+which is a one-way hash function based upon a modified DES algorithm;
+see the Unix man page for further details.  Possible uses include
+allowing Python scripts to accept typed passwords from the user, or
+attempting to crack Unix passwords with a dictionary.
+\index{crypt(3)}
+
+\begin{funcdesc}{crypt}{word\, salt} 
+\var{word} will usually be a user's password.  \var{salt} is a
+2-character string which will be used to select one of 4096 variations
+of DES.  The characters in \var{salt} must be either \code{.},
+\code{/}, or an alphanumeric character.  Returns the hashed password
+as a string, which will be composed of characters from the same
+alphabet as the salt.
+\end{funcdesc}
+
+The module and documentation were written by Steve Majewski.
+\index{Majewski, Steve}