Performs the equivalent of pthread_once()/ Basic Computer Science
Implement a function, one_time_init(control, init), that performs the equivalent of pthread_once(). The control argument should be a pointer to a statically allocated structure containing a Boolean variable and a mutex. The Boolean variable indicates whether the function init has already been called, and the mutex controls access to that variable. To keep the implementation simple, you can ignore possibilities such as init() failing or being canceled when first called from a thread (i.e., it is not necessary to devise a scheme whereby, if such an event occurs, the next thread that calls one_time_init() reattempts the call to init()).
