Aleph-Driver, comments in placehold()

* fix typo in element name (happened here: 8f62add)
* break comment message into two notefields of aleph (Z37_NOTE_1/2)
* both hold 50 characters each, VARCHAR2(50)
* post comment message into two fields
* comments longer than 100 characters will be lost (before, more than 50 were lost)
* see Issue swissbib/sbvf2#372 for more (in German)