Don't wait until the end to join threads in parallel_debug mode.

    (Chris Holmes, HP).

replaced by MpiDefault=mpich-gm.

due to short name being truncated to 16 bytes on some systems.

    "ProctrackType=proctrack/linuxproc")

for kill() when pid does not exist.

to start with instead of always using 1, which is prone to 
collisions.