model-checker : fix (again ..) DPOR for iSend/iRecv and Wait communications
- add rdv_cpy in s_smx_action_t structure. comm.rdv is used for
garbage collection and set to NULL when the communication matches
with another communication already pushed and waiting in the
mailbox.
- iSend/iRecv and Wait communications are independant if the
communications are not in the same mailbox. Otherwise, the
iSend/iRecv communication process issuer must be different of the
src_proc or dst_proc of the Wait communication, or, src_buff and
dst_buff of the communications must be different.
