Merge branch 'ab/die-errors-in-threaded'

Traditionally, the default die() routine had a code to prevent it
from getting called multiple times, which interacted badly when a
threaded program used it (one downside is that the real error may
be hidden and instead the only error message given to the user may
end up being "die recursion detected", which is not very useful).

* ab/die-errors-in-threaded:
  die(): stop hiding errors due to overzealous recursion guard