Get examples/ARM_security_properties to build given tight equality

Remove Globals.priming.

Also remove references to it in code that isn't being tested in the
regression checking build-sequence, and so is probably bit-rotted.

Provide numvariant version of variant, which behaves like

with_flag(Globals.priming,SOME "") (variant avoids)

Document change/incompatibility in release notes.

Fix ARM_security_properties for pretty-printing change

updated ARM model

holmade done OK