Add namelist value to initialize grid with a east or west open boundary and fix related issues.

[sergisiso]

The NemoLite2D namelist allows to initialize the domain with an open southern boundary with the parameter:
jphgr_msh = 1 ! type of grid (0: read in a data file; 1: setup with following parameters)

However, there are specific issues that may not be exposed in this grid (e.g. respecting the flather_v loop-carried dependency in j when all rows are in the same OpenMP chunck). These kind of issues could be tested by adding other grid mesh initialization options in jphgr_msh.

When doing this, a race condition in the C++OpenMP is exposed in the checksum value (and probably in the other implementations branched from it).

[sergisiso]

The namelist jphgr_msh with eastern open boundaries may also expose other issues (I got some NaN with long executions which also happen in Fortran and serial Fortran). In this issue I will just fix the mentioned race condition.

[arporter]

I've belatedly realised that I should have got you to include using this new jphgr functionality in the 'test suite' as part of #50. Maybe it can be added when we fix the other issues you've found?

[LonelyCat124]

Once this is done please let me know as I will copy it into Regent version as well.

Edit: Or if its done let me know and i'll do it :)

[sergisiso]

@LonelyCat124 The multiple options in the namelist and the fix of C++ OpenMP are in master now. The addition to the test-suite and a better fix in the kernel level will be done later on.

[LonelyCat124]

Ok, I'll try to add those options into the Regent namelist