fix-tests
[libc] Add implementations of pthread_equal and pthread_self.
[libc] Add a definition of pthread_attr_t and its getters and setters.
[libc][NFC] Remove the templatization from the linux implementation of thread.
[libc] Add pthread_create and pthread_join functions.
[libc] Add pthread_detach and thrd_detach.
[libc] Add the pthread_mutex_t type.
[libc] Add pthread_mutexattr_t type and its setters and getters.