Eliminate xmin from hash tag for predicate locks on heap tuples.

If a tuple was frozen while its predicate locks mattered,
read-write dependencies could be missed, resulting in failure to
detect conflicts which could lead to anomalies in committed
serializable transactions.

This field was added to the tag when we still thought that it was
necessary to carry locks forward to a new version of an updated
row.  That was later proven to be unnecessary, which allowed
simplification of the code, but elimination of xmin from the tag
was missed at the time.

Per report and analysis by Heikki Linnakangas.
Backpatch to 9.1.
plpgsql: Add new option print_strict_params.

This option provides more detailed error messages when STRICT is used
and the number of rows returned is not one.

Marko Tiikkaja, reviewed by Ian Lawrence Barwick
Make DISCARD SEQUENCES also discard the last used sequence.

Otherwise, we access already-freed memory.  Oops.

Report by Michael Paquier.  Fix by me.
Translation updates
Fix bugs in SSI tuple locking.

1. In heap_hot_search_buffer(), the PredicateLockTuple() call is passed
wrong offset number. heapTuple->t_self is set to the tid of the first
tuple in the chain that's visited, not the one actually being read.

2. CheckForSerializableConflictIn() uses the tuple's t_ctid field
instead of t_self to check for exiting predicate locks on the tuple. If
the tuple was updated, but the updater rolled back, t_ctid points to the
aborted dead tuple.

Reported by Hannu Krosing. Backpatch to 9.1.
TYPEALIGN doesn't work on int64 on 32-bit platforms.

The TYPEALIGN macro, and the related ones like MAXALIGN, don't work with
values larger than intptr_t, because TYPEALIGN casts the argument to
intptr_t to do the arithmetic. That's not a problem when dealing with
pointers or lengths or offsets related to pointers, but the XLogInsert
scaling patch added a call to MAXALIGN with an XLogRecPtr argument.

To fix, add wider variants of the macros, called TYPEALIGN64 and MAXALIGN64,
which are just like the existing variants but work with uint64 instead of
intptr_t.

Report and patch by David Rowley, analysis by Andres Freund.
docs:  update release notes for 8.4.18, 9.0.14, 9.1.10, 9.2.5, 9.3.1
Update instructions on creating minor release notes.
Additional instructions on minor release note creation.
Auto-tune effective_cache size to be 4x shared buffers
unaccent:  mark unaccent() functions as immutable

Suggestion from Pavel Stehule
docs:  clarify references to md5 hash and md5 crypt in pgcrypto docs

Suggestion from Richard Neill
Update postgres.conf.sample for effective_cache_size's new default
Allow drop-index-concurrently-1 test to run at any isolation level.

It previously reported failure at REPEATABLE READ and SERIALIZABLE
transaction isolation levels for make installcheck.
doc:  Fix typo in effective_cache_size patch
Fix C comment in check_effective_cache_size()
Move new effective_cache_size function

Previously set_default_effective_cache_size() could not handle fork,
non-fork, and bootstrap cases.
Again move function where we set effective_cache_size's default
Adjust the effective_cache_size default for standalone backends
Centralize effective_cache_size default setting