docs: error for adding  _validated_ domains for existing uses

Report by David G Johnston
C comments: adjust execTuples.c for new structure

Report by Peter Geoghegan
doc:  mention more changes needed to use huge pages

Report by Laurence Parry
doc:  mention TM is ignored for to_date/to_timestamp()

Report by Goulven Guillard
psql: Fix \? output alignment

This was inadvertently changed in commit c64e68fd.
doc: Fix copy-and-paste mistakes
doc: Improve ALTER VIEW / SET documentation

The way the ALTER VIEW / SET options were listed in the synopsis was
very confusing.  Move the list to the main description, similar to how
the ALTER TABLE reference page does it.
Fix typo in docs.

Shigeru Hanada
Fix deadlock with LWLockAcquireWithVar and LWLockWaitForVar.

LWLockRelease should release all backends waiting with LWLockWaitForVar,
even when another backend has already been woken up to acquire the lock,
i.e. when releaseOK is false. LWLockWaitForVar can return as soon as the
protected value changes, even if the other backend will acquire the lock.
Fix that by resetting releaseOK to true in LWLockWaitForVar, whenever
adding itself to the wait queue.

This should fix the bug reported by MauMau, where the system occasionally
hangs when there is a lot of concurrent WAL activity and a checkpoint.
Backpatch to 9.4, where this code was added.