Approved by:	re (implicit)

This commit was manufactured to restore the state of the 8.2-RELEASE image.

In current code, statically initialized and destroyed object have
same null value, the code can not distinguish between them, to
fix the problem, now a destroyed object is assigned to a non-null
value, and it will be rejected by some pthread functions.
PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP is changed to number 1, so that
adaptive mutex can be statically initialized correctly.

Remove unused source.

The __hidden definition is provided by sys/cdefs.h.

a reader lock.

Use _SIG_VALID instead of expanded form of the macro.

PR:		135462
Approved by:	re (kib)
Nod timeout:	davidxu

Reimplement pselect() in kernel, making change of sigmask and sleep atomic.

MFC r198538:
Move pselect(3) man page to section 2.

Work-around a race condition on ia64 while unlocking a contested lock.

Let fall down in the hard path (thus handling shared waiters wakeup
correctly) for the shared waiters also in the rwlock held in shared mode
as well, fixing possible deadlocks.

Please note that this is a special condition as we want this fix in
before RC2 as we assume it is critical and so it has been handled
as an instant-merge.  For the STABLE_7 branch, 1 week before the MFC
is assumed.

Approved by:	re (kib)