Update link to the FIPS PUB 180-1 (PDF is available, but not PostScript).

Doc/lib/libsha.tex

@@ -53,6 +53,6 @@ A sha object has all the methods the md5 objects have, plus one:
             \citetitle[http://csrc.nist.gov/fips/fip180-1.txt]{Secure
             Hash Standard}, published in April of 1995.  It is
             available online as plain text (at least one diagram was
-            omitted) and as PostScript at
-            \url{http://csrc.nist.gov/fips/fip180-1.ps}.}
+            omitted) and as PDF at
+            \url{http://csrc.nist.gov/fips/fip180-1.pdf}.}
 \end{seealso}