lib: NativeString is an extern class (and not a special case)

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
lib/serialization: accept Text as input

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
lib: intro the c module

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
lib: intro the mpi module

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
examples: add a basic usage of mpi

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
examples: add README and example host file to mpi example

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
tests: add test for module C

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
Merge: Message Passing Interface (MPI) in Nit and partial C language module

mpi.nit brings parallel programming to Nit using Message Passing Interface with OpenMPI. Will be used to implement a distributed tester.

c.nit offers low-level structures for performance critical code. More structure and services could be added as needed.

Warning: Does not yet pass all tests on nitg-e, will need to solve the "No provided declaration" error on extern classes with virtual types. I'll update this PR to solve this soon.

Pull-Request: #548
Reviewed-by: Jean Privat <jean@pryen.org>