Merge branch 'ci/ralf/ghostcell' into 'master'

README.md

_CoqProject

theories/lang/notation.v

theories/lifetime/lifetime.v

theories/lifetime/lifetime_sig.v

theories/lifetime/meta.v

theories/lifetime/model/creation.v

theories/lifetime/model/definitions.v

theories/lifetime/model/primitive.v

theories/typing/bool.v

theories/typing/borrow.v

theories/typing/cont.v

theories/typing/cont_context.v

theories/typing/examples/nonlexical.v

theories/typing/fixpoint.v

theories/typing/function.v

theories/typing/int.v

theories/typing/lft_contexts.v

theories/typing/lib/arc.v

theories/typing/lib/brandedvec.v