[nomaster] macro errors now always have positions

Back then when I implemented macros for inclusion in trunk (Spring 2012),
partest didn't support the _1, _2, ... convention for neg tests, so I had
to use toolboxes to test macro-generated exceptions.

Unfortunately toolboxes aren't very good with positions (mostly because
their inputs are almost always constructed without corresponding sources)
so I didn't notice that errors signalizing about macro-generated
exceptions actually don't carry positions with them because of a typo.

This patch fixes the oversight, but it doesn't need to be ported to master,
because over there everything's already fixed by one of the backports
from macro paradise.