- previously built the entire adjacency table (full communication!)
  but this is only strictly needed when using 'scheduled' as the
  default communication mode. For blocking/nonBlocking modes this
  information is not necessary at that point.

  The processorTopology::New now generally creates a smaller amount of
  data at startup: the processor->patch mapping and the patchSchedule.

  If the default communication mode is 'scheduled', the behaviour is
  almost identical to previously.

- Use Map<label> for the processor->patch mapping for a smaller memory
  footprint on large (ie, sparsely connected) cases. It also
  simplifies coding and allows recovery of the list of procNeighbours
  on demand.

- Setup the processor initEvaluate/evaluate states with fewer loops
  over the patches.

========
BREAKING: procNeighbours() method changed definition

- this was previously the entire adjacency table, but is now only the
  processor-local neighbours. Now use procAdjacency() to create or
  recover the entire adjacency table.

  The only known use is within Cloud<ParticleType>::move and there it
  was only used to obtain processor-local information.

  Old:
      const labelList& neighbourProcs =
          mesh.globalData().topology().procNeighbours()[Pstream::myProcNo()];

  New:
      const labelList& neighbourProcs =
          mesh.globalData().topology().procNeighbours();

      // If needed, the old definition (with communication!)
      const labelListList& connectivity =
          mesh.globalData().topology().procAdjacency();