Use temporary files to store output of the command in perl tesh
Avoids deadlocking when large data is sent to/from pipes (see tesh test IO-bigsize)
add background commands support + correct error code for output mismatch
not implicit on all systems
we now only have one build mode for win, as mc is irrelevant for now
try to speed up a bit testing by using all available cores in the slaves
when parallel ctests are performed, using the default tracing filename may cause trouble.