Jonny Lamb authored Dec 14, 2018 and Olivier Crête committed Dec 18, 2018

I copied `error-after` to make the `eos-after` property, but it turned
out there were some problems with that one, so this patch: adds
separate counters (so setting to NULL and reusing the element will
still work); clarifies the properties' min values; and reports an
error when both are set.