Added lost docs for crypt module.
diff --git a/Doc/lib/libunix.tex b/Doc/lib/libunix.tex
index fe92d97..895c6e5 100644
--- a/Doc/lib/libunix.tex
+++ b/Doc/lib/libunix.tex
@@ -18,6 +18,9 @@
 \item[grp]
 --- The group database (\code{getgrnam()} and friends).
 
+\item[crypt]
+--- The (\code{crypt()} function used to check Unix passwords).
+
 \item[dbm]
 --- The standard ``database'' interface, based on \code{ndbm}.