* include/std/shared_mutex (shared_timed_mutex): Add comments to
explain the logic in the non-pthread_rwlock_t version.
(_Mutex): Remove redundant type.
(_M_n_readers): Rename to _S_max_readers.
(_M_write_entered, _M_readers): New convenience functions.
(lock, lock_shared, try_lock_shared, unlock_shared): Use convenience
functions. Use predicates with condition variables. Simplify bitwise
operations.
(try_lock_for, try_shared_lock_for): Convert duration to time_point
and call try_lock_until or try_shared_lock_until respectively.
(try_lock_until, try_shared_lock_until): Wait on the condition
variables until the specified time passes.
(unlock): Add Debug Mode assertion.
(unlock_shared): Add Debug Mode assertion.
* testsuite/30_threads/shared_timed_mutex/try_lock/3.cc: New.
From-SVN: r221970
43b0e124e4