DragonFlyBSD

The following program when compiled with -pthread on DragonFly fails with assertion 22, while it works on Linux:

#include <assert.h>
#include <pthread.h>

int main() {
pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
assert(pthread_mutex_destroy(&lock) == 0); // returns EINVAL (22)
}

While when it goes through a lock/unlock cycle or pthread_mutex_init() is called before,
the pthread_mutex_destroy() does not fail with EINVAL:

int main() {
pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_init(&lock, NULL);
assert(pthread_mutex_destroy(&lock) == 0); // OK
}

I propose the attached patch to return success if pthread_mutex_destroy() is called
for the PTHREAD_MUTEX_INITIALIZER case.