Fix test that did not do what was intended
Add support for user-friendly crash messages
Fixes for exit signals
Ensure that deadlocked processes unregister their names

It is impossible for a PID to be checked for status before it is generated, so
(re)starting a process in the 'running' state should be ok.
Allow atoms other than normal to be considered normal exit reasons
More race info for erlang built-ins
More soft crashing
Fixes for link/1 and demonitor/1
Merge remote-tracking branch 'upstream-new/master' into master-new

Conflicts:
	Makefile
	src/concuerror_callback.erl
	src/concuerror_options.erl
	src/concuerror_scheduler.erl