Several new expression forms are supported to derive the individual values defined by
Old pre-v0.15 changelogs (very likely stale and incomplete)
Depend on ppxlib instead of (now deprecated) ppx_core, ppx_driver and ppx_type_conv.
use the new context-free API
Fix the META. ppx_bin_prot was not previously treated as a ppx_deriving plugin, which was causing problems
Minor changes, nothing worth mentionning.