GitLab

All to support Trac #2431

'debugger gives "Can't unify" when stopped at an exception'

Avoids an ambiguous type variable with extensible extensions

":load M" now complains if M.hs doesn't contain module M, but ':load
M.hs' does not.  This seems reasonable to me, but there's potential
for confusion.  I'm not sure how to improve the situation though.