org: fix two links

Fixes #150.

* doc/org/tut.org: Fix links to notebooks.
* tests/sanity/ipynb.pl: Catch this type of errors in the future.

doc/org/tut.org

@@ -63,6 +63,6 @@ real notebooks instead.
   automaton
 - [[https://spot.lrde.epita.fr/ipynb/ltsmin.html][=ltsmin.ipynb=]] minimal test for loading a DiVinE model using
   the LTSmin interface.
-- [[https://spot.lrde.epita.fr/ipynb/ltsmin.html][=word.ipynb=]] example for the =twa_run= and =twa_word= classes.
-- [[https://spot.lrde.epita.fr/ipynb/ltsmin.html][=highlighting.ipynb=]] shows how to highlight states or edges in
+- [[https://spot.lrde.epita.fr/ipynb/word.html][=word.ipynb=]] example for the =twa_run= and =twa_word= classes.
+- [[https://spot.lrde.epita.fr/ipynb/highlighting.html][=highlighting.ipynb=]] shows how to highlight states or edges in
   automata.

tests/sanity/ipynb.pl

@@ -44,13 +44,18 @@ my $exit_status = 0;
 my %seen;
 while (<FD>)
 {
-    if (m:\]\[=([\w-]+\.ipynb)=\]\]:)
+    if (m:/([\w-]+)\.html\]\[=([\w-]+\.ipynb)=\]\]:)
     {
 	# print "$1 documented";
-	$seen{$1} = 1;
-	unless (-f "$dir/$1")
+	$seen{$2} = 1;
+	unless (-f "$dir/$2")
 	{
-	    print STDERR "notebook $1 mentioned in tut.org does not exist";
+	    print STDERR "notebook $2 mentioned in tut.org does not exist";
+	    $exit_status = 1;
+	}
+	if ("$1.ipynb" ne "$2")
+	{
+	    print STDERR "in tut.org, notebook $2 links to $1.html";
 	    $exit_status = 1;
 	}
     }