The disp and layr sections have new v19 layouts, to support the Keyman
OSK requirements for epic/embed-osk-in-kmx. This supports writing the
new versions of these sections in Developer and loading them into Core,
doing transformations where necessary so that Core always works with v19
structures after load.
This does not implement the transformations required to support the OSK
APIs; that will be implemented in a follow-up PR. Nor is support for
writing the OSK data from source .kvks and .keyman-touch-layout
supported; this is just the scaffolding for supporting the structures in
the KMX+ data.
Test-bot: skip