bors f3c923a13a Auto merge of #76645 - fusion-engineering-forks:windows-lock, r=kennytm
Small cleanups in Windows Mutex.

 - Move `held` into the boxed part, since the SRW lock implementation does not use this. This makes the Mutex 50% smaller.
 - Use `Cell` instead of `UnsafeCell` for `held`, such that `.replace()` can be used.
 - Add some comments.
 - Avoid creating multiple `&mut`s to the critical section object in `ReentrantMutex`.
2020-09-17 19:23:58 +00:00
..