Next chunk, write up until discussion of problems
Add ConcState and CONCSTATE into a mutual block
Add Locks module
Rename Main.main to test to avoid name clashes
Add "initialisation" function to Locks
Add debug printing in Locks
HACK: temporary work-around to include Locks in ConcState
Some further progress/fixes in report
Generalise ConcState effect, use real locking

* generalises ConcState to GenConcState which is then parametrised over a
  resource interpreter (hence ConcState becomes a GenConcState with the default
  interpreter).
* uses Locks for "real" shared resource access/locking/unlocking
* also removes the need for most proofs using the `{auto p: ... }` automatic
  proof tactic
Clean up code + fix compilation
Generalise to incrementing `nth`s resource