user:message_hook(+Term, +Kind, +Lines) is semidet[multifile, library(pengines_io)]
Send output from print_message/2 to the pengine. Messages are embedded in a <pre class=msg-Kind></pre> environment.
 user:message_hook(+Severity, +Message, +Lines) is semidet[multifile, library(plunit)]
Redefine printing some messages. It appears SICStus has no way to get multiple messages at the same line, so we roll our own. As there is a lot pre-wired and checked in the SICStus message handling we cannot reuse the lines. Unless I miss something ...