PRESSURE_RECONSTRUCTION_SCHEME=2 not available in non-Boussinesq mode

[awallcraft]

When using ALE, the default, PRESSURE_RECONSTRUCTION_SCHEME=1, is almost always applied. This is PLM vertical reconstruction of T&S for the FV pressure gradient.

There is an option to instead use PPM vertical reconstruction (PRESSURE_RECONSTRUCTION_SCHEME=2) and this seems to provide some advantages in Boussinesq test cases. However, it is not available in non-Boussinesq mode:

          call MOM_error(FATAL, "PressureForce_FV_nonBouss: "//&
                         "int_spec_vol_dp_generic_ppm does not exist yet.")