ENH: improved isolation of MPI access in Pstreams

- refactor as an MPI-independent base class.

  Add bufferIPC{send,recv} private methods for construct/destruct.
  Eliminates code duplication from two constructor forms and reduces
  additional constructor definitions in dummy library.

- add PstreamBuffers access methods, refactor common finish sends
  code, tweak member packing

ENH: resize_nocopy for processorLduInterface buffers

- content is immediately overwritten

STYLE: cull unneeded includes in processorFa*

- handled by processorLduInterface

src/finiteArea/fields/faPatchFields/constraint/processor/processorFaPatchField.C

@@ -28,8 +28,6 @@ License
 
 #include "processorFaPatchField.H"
 #include "processorFaPatch.H"
-#include "IPstream.H"
-#include "OPstream.H"
 #include "transformField.H"
 
 // * * * * * * * * * * * * * * * * Constructors * * * * * * * * * * * * * * //