* dcrt0.cc (cygwin_finished_initializing): Copy _mtinterf on fork;
* fork.cc (fork_child): fixup thread-related structures after fork;
* thread.cc (MTinterface::Init): Initialise the new mutex, condition and semaphore lists.
(MTinterface::fixup_after_fork): Iterate through each list and fixup the objects.
(pthread_cond::pthread_cond): Add this to the condition list.
(pthread_cond::~pthread_cond): Remove this from the condition list.
(pthread_cond::fixup_after_fork): Recreate as best we can the pre-fork state.
(pthread_mutex::pthread_mutex): Add this to the mutex list.
(pthread_mutex::~pthread_mutex): Remove this from the mutex list.
(pthread_mutex::fixup_after_fork): Recreate as best we can the pre-fork state.
(semaphore::semaphore): Store the initial value, and add this to the semaphore list.
(semaphore::~semaphore): Remove this from the semaphore list.
(semaphore::Post): Increment the current semaphore value.
(semaphore::TryWait): Decrement the current semaphore value.
(semaphore::Wait): Ditto.
(semaphote::fixup_after_fork): Recreate the pre-fork state as best we can.
* thread.h (pthread_mutex): New members to allow fixup_after_fork.
(pthread_cond): Ditto.
(semaphore): Ditto.
(MTinterface): New list heads for tracking conds and semaphores.
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