cleanup after martin's cleanup
deactivate test that actually needs MPI_Type_get_envelope
model-checker : save and restore file descriptors
model-checker : comment debug printf
[mc] Fix FD checkpoint/restore
replace xbt_dynar_member by xbt_dynar_search_or_negative in this test.

There is a weird bug with xbt_dynar_member on some systems.
When an exception is raised, backtracking mechanism of libc6 can cause segfaults (and valgrind complains quite a lot, even on systems where it does not crash)
Is this related to https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=735090 ?

example obtained stack
 Invalid read of size 4
    at 0x476E383: backtrace (backtrace.c:141)
    by 0x43DC03B: xbt_backtrace_current (backtrace_linux.c:84)
    by 0x43DB200: xbt_dynar_search (dynar.c:474)
    by 0x43DB31F: xbt_dynar_member (dynar.c:511)
    by 0x80494A3: test_launcher (host_on_off_processes.c:35)
    by 0x43C889E: smx_ctx_sysv_wrapper (smx_context_sysv.c:187)
    by 0x46B2BDA: makecontext (makecontext.S:87)

As functionality is the same, using the exception-less version of xbt_dynar_member should avoid the problem, until we find out more about it