Hack in support for TI exams

This just adds an additional crawl check for AlteKlausuren. This is not
present on the root site but at the suffix `/Klausuren`.
Example config:

```py
 # The "Klausur" needs to be copied verbatim!
ti.synchronize("Klausur", "sync dir name",
               transform=ro_19_klausur_transform, filter=ro_19_klausur_filter)
```

PFERD/ti.py

@@ -67,6 +67,9 @@ class Ti:
         if soup.find(href="./Tutorien/Tutorien.php"):
             logger.info("Found Tutorien/")
             available["Tutorien"] = "/Tutorien/"
+        if soup.find(href="./AlteKlausuren/AlteKlausuren.php"):
+            logger.info("Found AlteKlausuren/")
+            available["AltKlausuren"] = "/AlteKlausuren/"
 
         return available