Fix standard error handling
Need to make sure $STACK
is correct and that $ETRAP
is solid. This should be easier once we finish replacing direct access to ierr
with function calls to merr_raise
and merr
, this should be easier, as the values for the $STACK
pseudo-function should be able to be populated in merr_raise
, based on the nstx
stack index, rather than being populated unreliably in other scattered locations in the FreeM codebase.