Bug #6293 - Cannot regrade a question when a teacher has added a comment with a ...

Bug #6293 - Cannot regrade a question when a teacher has added a comment with a ' - Merged from MOODLE_16_STABLE.\r\rStupid, wreched, datalib.\r\rWhy can't datalib take care of addslashes, so the whole of the rest of the code can forget about it? That is how a database abstraction layer should work.\r\rI know, it is pointless to moan about it, but it has just cost me 3 hours, so I feel I have earned the right to moan.