1.7.0

• lazy deserialization regime for message fields and associated option -fieldmod
  Refer to "Evaluation regime" section in doc/language-mapping.md
• improved codegen for monomorphic record types
• -mli option to generate .mli signatures
• -export-type-io option to export monomorphic record type
  (de)serialization functions and allow to reference the type in other
  protocols
• -assume-subsets option to enable cross-protocol subsets of messages
  (use in proto for whose messages subsets will be created)
• support for extlib 1.7.8