+ SIMIX:
+ * Relocation of the context module from XBT to SIMIX.
+ (the context were decoupled from the simix processes, duplicating a lot of code)
+ => a lot of code was factorized
+ - less overhead is introduced during scheduling
+ - simpler API for the context factory
+ - the logic for process creation,destruction and manipulation was simplified
+ * Simplification of the s_smx_process_t data structure.
+ => accesing the simix level data associated to a process is faster now,
+ and the code is a lot more readable.
+