Returns the identifier of the calling thread.
1 – C Binding
    #include <tis.h>
    pthread_t
    tis_self (void);
2 – Arguments
None
3 – Description
    This routine allows a thread to obtain its own thread identifier.
    This value becomes meaningless when the thread is destroyed.
    Note that the initial thread in a process can "change identity"
    when thread system initialization completes-that is, when the
    multithreading run-time environment is loaded.
4 – Return Values
Returns the thread identifier of the calling thread.
5 – Associated Routines
pthread_create()