openfoam reader ignores embedded 32/64-bit information

The additional arch information in FoamFile header provides information about the precision of the contents (integer and floats). However, most of the reader doesn't handle this properly and blindly applies the values from the GUI in various places. For mixed workflows this becomes as complete disaster (ie, SEGFAULT).

For an example of a "mixed workflow":

• surface preparation and meshing (snappyHexMesh) with 64-bit labels and double precision
• initial calculation with the same settings
• restart and run calculation with mixed precision - field storage in single precision, with the linear solver running in double precision.

Since the internal file representation changes between time steps, there is no GUI setting that works.