monitor tracee and local tracer to avoid "dead" processes

this may be removed at some point, it's very brutal. But when you
write some code, it may happen (it "may"!!) that *sometimes* the
code does not work and crashes. In thoses cases I prefer the
local tracer (or the tracee) to go away immediately without even
thinking about it maybe still running in the background.

In case of monitoring (as opposed to debugging) maybe it's preferable
to let the process live its life as it wants.

Time will tell.