* thread.h (pthread_cond): New element cond_access to allow atomic broadcasts.
* thread.cc (pthread_cond::pthread_cond): Initialise cond_access.
(pthread_cond::~pthread_cond): Destroy cond_access.
(pthread_cond::Broadcast): Use cond_access.
(pthread_cond::Signal): Use cond_access.
(pthread_cond_wait): Use cond_access.
(pthread_cond_timedwait): Use cond_access.