[SMPI] (FIRST PATCH) Remove 'getPid() - 1' arithmetic from SMPI.

[SMPI] (FIRST PATCH) Remove 'getPid() - 1' arithmetic from SMPI.

THIS COMMIT WILL NOT BUILD PROPERLY OR HAS FAILING TESTS. I decided to split up
a huge commit into several logical chunks in order to make things easier to read.

The 'getPid() - 1' expressions were the (temporary) replacement for smpi_process()->index() but it's better
to remove it completely: This is often confused for being an MPI rank
although it is not (ranks depend on the communicator in use).
Also, process id 0 is exclusively the maestro so we should not artificially
pretend we start counting from 0 when we're clearly not. So now we don't have to
say that 'process with id 1 has index 0'.

This patch substitutes almost exclusively 'getPid() - 1' computations with
just 'getPid()'. There are a few other replacements, especially in the smpi_win.cpp,
where former commits introduced logically wrong usage of 'comm_->rank()'.

The next few commits after this should also deal with a similar problematic.'