This will ensure that tamed does not stall while e.g. make is still
running. This makes TAMED_STALL_SECONDS almost useless; maybe it'll be
removed in future versions.
* bin/tame (TAMED_SPAWNER_PID): Export variable.
* bin/tamed (TAMED_SPAWNER_PID): New variable, default to PPID.
(spawner-dead): New function.
(stall-monitor): Use it.
(usage): Update documentation.
* build-aux/Makefile.am: Set TAMED_SPAWNER_PID to own id and export.
079d1dcfaf