v0.1.34

Add the release workflow mpl never had

mpl was registered in the CLI and tagged v0.1.34 with only a ci.yml, so the
tag pushed and nothing built or published. Every other construction engine has
this file, and ifp's copy states the rule I broke: it has to exist BEFORE the
engine is added to the install list, because an engine listed with no release
behind it turns every install into a 404.

release-suite.sh reported it PENDING rather than claiming success, which is
the only reason it was caught.

Modelled on ifp's, which is itself modelled on opendb's, for the same reason:
mpl writes the database through vyges-opendb, which statically links libodb
from source, so this is unix-only and native per target. mpl patches loom as
well as the opendb pair, so loom gets a checkout too -- a patched path with no
checkout is a hard failure, not a fallback to git.