L13 : array declarations in parallel routines

Parallel routines (those processing a list of NPROMA blocks) should wrap their field data into Field API objects.

In particular the legacy data representation for model state (PGMV/PGFL arrays) should be considered obsolescent and replaced by YDVARS wherever possible.

Parallel routines should never declare an array that will be involved in calculations (ie passed to NPROMA routines or used in OpenMP sections).