Alter string to render properly in bit bucket

[Jeremy Hopkins]

Mary evans reported a problem with line 536 of renderer.php:

https://moodle.org/mod/forum/discuss.php?d=326234#p1324361

This is not a bug just that bitbucket does not recognise the escape strings in:

return "<div class=\"$type\">$message</div>";

Will correct so it makes it easier to view this file online

[Jeremy Hopkins]

Fix #380

→ <<cset 7eb53cc400ff>>