Sorting all output for the external tests.

Let's see how this goes. The script keeps comments at the beginning.

testing/scripts/diff-canonifier-external

@@ -6,3 +6,4 @@
     | `dirname $0`/diff-remove-uids \
     | `dirname $0`/diff-remove-mime-types \
     | `dirname $0`/diff-remove-x509-names \
+    | `dirname $0`/diff-sort

testing/scripts/diff-sort

@@ -0,0 +1,19 @@
+#! /usr/bin/env bash
+#
+# A diff canonifier that sorts all lines but keeps all comments
+# at the top. It also adds a note at the beginning as a reminder
+# that the output has been sorted.
+
+if [ "$TMP" == "" ]; then
+    TMP=/tmp
+fi
+
+tmp=$TMP/`basename $0`.$$.tmp
+
+cat >$tmp
+
+echo "### NOTE: This file has been sorted with `basename $0`."
+cat $tmp | grep ^#
+cat $tmp | grep -v ^# | sort -s
+
+rm -f $tmp