Condition.notify only does nothing if no thread is waiting

Signed-off-by: Mattias Andrée <maandree@operamail.com>
fix ordered join and add test

Signed-off-by: Mattias Andrée <maandree@operamail.com>
test signal fragments and unjoining

Signed-off-by: Mattias Andrée <maandree@operamail.com>
derp

Signed-off-by: Mattias Andrée <maandree@operamail.com>
test concurrently

Signed-off-by: Mattias Andrée <maandree@operamail.com>