enhanced parallel statuses and semifar operators

[pigay]

To reproduce this bug:

mpiexec -n 3 tests/newtonfield3parallel -np 18 -pr 8 -s 1 -dist plummer -translation rotate -semifar 0

output contains:

1 : Field simulation error: 15 relative=(7.476370e-02) pos=(0.002755,-0.639106,0.189065)
                        computed=(0.080037,0.233377,-0.171765) exact=(0.061106,0.223813,-0.176848)
1 : Field simulation error: 12 relative=(5.936650e-02) pos=(0.606376,-0.425608,0.172685)
                        computed=(-0.138039,0.061302,-0.174424) exact=(-0.150697,0.055358,-0.176744)
[...]
0 : Field simulation error: 7 relative=(1.554696e-01) pos=(-1.079993,-2.253779,-0.102440)
                        computed=(0.034581,0.108844,-0.012131) exact=(0.047088,0.125305,-0.009334)
0 : Field simulation error: 8 relative=(1.045137e-01) pos=(-1.939900,-0.464095,-0.331684)
                        computed=(0.165692,0.035794,-0.006659) exact=(0.184773,0.034840,-0.002053)

This bug first appears in b58dee6