libpq:  change PQconndefaults() to ignore invalid service files

Previously missing or invalid service files returned NULL.  Also fix
pg_upgrade to report "out of memory" for a null return from
PQconndefaults().

Patch by Steve Singer, rewritten by me
Update C comment for pg_fe_getauthname

This function no longer takes an argument.
C comment:  again update comment for pg_fe_sendauth for error cases
Fix full-page writes of internal GIN pages.

Insertion to a non-leaf GIN page didn't make a full-page image of the page,
which is wrong. The code used to do it correctly, but was changed (commit
853d1c3103fa961ae6219f0281885b345593d101) because the redo-routine didn't
track incomplete splits correctly when the page was restored from a full
page image. Of course, that was not right way to fix it, the redo routine
should've been fixed instead. The redo-routine was surreptitiously fixed
in 2010 (commit 4016bdef8aded77b4903c457050622a5a1815c16), so all we need
to do now is revert the code that creates the record to its original form.

This doesn't change the format of the WAL record.

Backpatch to all supported versions.
Don't include unused space in LOG_NEWPAGE records.

This is the same trick we use when taking a full page image of a buffer
passed to XLogInsert.
Fix whitespace
doc: split long query into multiple lines

Report from Erik Rijkers
build:  pass EXTRA_REGRESS_OPTS to secondary regression tests

Christoph Berg
Avoid resetting Xmax when it's a multi with an aborted update

HeapTupleSatisfiesUpdate can very easily "forget" tuple locks while
checking the contents of a multixact and finding it contains an aborted
update, by setting the HEAP_XMAX_INVALID bit.  This would lead to
concurrent transactions not noticing any previous locks held by
transactions that might still be running, and thus being able to acquire
subsequent locks they wouldn't be normally able to acquire.

This bug was introduced in commit 1ce150b7bb; backpatch this fix to 9.3,
like that commit.

This change reverts the change to the delete-abort-savept isolation test
in 1ce150b7bb, because that behavior change was caused by this bug.

Noticed by Andres Freund while investigating a different issue reported
by Noah Misch.
Clear retry flags properly in replacement OpenSSL sock_write function.

Current OpenSSL code includes a BIO_clear_retry_flags() step in the
sock_write() function.  Either we failed to copy the code correctly, or
they added this since we copied it.  In any case, lack of the clear step
appears to be the cause of the server lockup after connection loss reported
in bug #8647 from Valentine Gogichashvili.  Assume that this is correct
coding for all OpenSSL versions, and hence back-patch to all supported
branches.

Diagnosis and patch by Alexander Kukushkin.
Fix improper abort during update chain locking

In 247c76a98909, I added some code to do fine-grained checking of
MultiXact status of locking/updating transactions when traversing an
update chain.  There was a thinko in that patch which would have the
traversing abort, that is return HeapTupleUpdated, when the other
transaction is a committed lock-only.  In this case we should ignore it
and return success instead.  Of course, in the case where there is a
committed update, HeapTupleUpdated is the correct return value.

A user-visible symptom of this bug is that in REPEATABLE READ and
SERIALIZABLE transaction isolation modes spurious serializability errors
can occur:
  ERROR:  could not serialize access due to concurrent update

In order for this to happen, there needs to be a tuple that's key-share-
locked and also updated, and the update must abort; a subsequent
transaction trying to acquire a new lock on that tuple would abort with
the above error.  The reason is that the initial FOR KEY SHARE is seen
as committed by the new locking transaction, which triggers this bug.
(If the UPDATE commits, then the serialization error is correctly
reported.)

When running a query in READ COMMITTED mode, what happens is that the
locking is aborted by the HeapTupleUpdated return value, then
EvalPlanQual fetches the newest version of the tuple, which is then the
only version that gets locked.  (The second time the tuple is checked
there is no misbehavior on the committed lock-only, because it's not
checked by the code that traverses update chains; so no bug.) Only the
newest version of the tuple is locked, not older ones, but this is
harmless.

The isolation test added by this commit illustrates the desired
behavior, including the proper serialization errors that get thrown.

Backpatch to 9.3.