langref/errorset: Replace subset description with union

The previous language using subsets was really just stating a couple
of the properties of the union of a group of sets, and with a minor
error at that.

langref/errorset: Replace subset description with union

The previous language using subsets was really just stating a couple
of the properties of the union of a group of sets, and with a minor
error at that.

langref/errorset: Replace subset description with union

The previous language using subsets was really just stating a couple
of the properties of the union of a group of sets, and with a minor
error at that.

langref/errorset: Replace subset description with union

The previous language using subsets was really just stating a couple
of the properties of the union of a group of sets, and with a minor
error at that.

langref/errorset: Replace subset description with union

The previous language using subsets was really just stating a couple
of the properties of the union of a group of sets, and with a minor
error at that.

langref/errorset: Replace subset description with union

The previous language using subsets was really just stating a couple
of the properties of the union of a group of sets, and with a minor
error at that.

langref/errorset: Replace subset description with union

The previous language using subsets was really just stating a couple
of the properties of the union of a group of sets, and with a minor
error at that.

langref/errorset: Replace subset description with union

The previous language using subsets was really just stating a couple
of the properties of the union of a group of sets, and with a minor
error at that.

langref/errorset: Replace subset description with union

The previous language using subsets was really just stating a couple
of the properties of the union of a group of sets, and with a minor
error at that.

langref/errorset: Replace subset description with union

The previous language using subsets was really just stating a couple
of the properties of the union of a group of sets, and with a minor
error at that.