There's no libnettle udeb.
-Index: xorg-server/configure.ac
-===================================================================
---- xorg-server.orig/configure.ac 2013-08-02 20:15:25.471466837 +0200
-+++ xorg-server/configure.ac 2013-08-02 20:17:12.875999417 +0200
-@@ -1433,7 +1433,7 @@
+--- a/configure.ac
++++ b/configure.ac
+@@ -1623,7 +1623,7 @@ fi
if test "x$with_sha1" = xlibnettle; then
AC_DEFINE([HAVE_SHA1_IN_LIBNETTLE], [1],
[Use libnettle SHA1 functions])