JMLCoq 8.15.0 maintenance release

Maintenance release with Coq 8.15 and 8.16 compatibility, with the following changes:

• fix deprecations
• port to Coq 8.15 and beyond
• documentation additions

JMLCoq 8.13.0 maintenance release

Maintenance release with Coq 8.13 compatibility, with the following features:

• fix deprecations
• port to Coq 8.13 and beyond

JMLCoq 8.12.0 maintenance release

Maintenance release after move to coq-community, with Coq 8.12 compatibility, with the following features:

• port to Coq 8.9 and later
• fix deprecations
• optional support for building with Dune