Fix deadlock, introduce another bug

Fix deadlock, introduce another bug

The deadlock would happen in the case that 2 philosophers starve at
almost the same time. Their starvation_watchers both leave their loop
and one continues as usual - posting death and turning its philo dead.

The philos, that didn't yet turn dead through the end watcher but
the one starvation watcher that triggered but didn't win the terminal
has the philo locked (it would turn the philo dead if it got the term)
but that makes the end watcher unable to make the philo dead.

This is solved by introducing another lock so that the philo is locked
even though the end watcher is not. The problem now is that neither
normal (not double) death ends the philos nor the "well fed" end.