Fixes#41.
OpenMP 4.5 does not require the map clauses on the target region
if the data has been previously defined using unstructured data
enter/exit clauses. Removing this clauses works fine with the
Clang compiler, however we noticed issues with the Cray compiler.
The issue is that the Cray compiler does not block the target
region "kernel calls" and so the timing is incorrect. This was
not noticed before due to the presence of the map clauses.
For now, we have had to add an update from clause of a scalar
value to ensure that the kenel blocks. It is hoped that we can
remove this in due course. But in the vein of showing how the
models work we want to keep the minimum required correct code
(which is without the map clause) but need the code to also
work correctly.
This fixes#42. On the Clang compiler, the map clause should appear
before the reduction clause to ensure that the evaluation order
of the clauses copies the reduction value back correctly.
This makes no difference with the Cray compiler.
