I planned to use them to simplify wsat_le, but it did not turn out to be simpler.

This reverts commit 5161e463.

Since ssr ad273277 the Global Set Bullet Behavior in modures.base
should do the job.

For consistency, let's deal with autosubst in the same way as with
ssreflect. The user should install it somewhere itself.

This should be documented and possibly discussed later.