In [common_threads.h](https://github.com/remzi-arpacidusseau/ostep-code/blob/master/include/common_threads.h), why are some of the macros duplicated—e.g. `Pthread_mutex_lock` and `Mutex_lock`?
In common_threads.h, why are some of the macros duplicated—e.g.
Pthread_mutex_lockandMutex_lock?