Track spinlock delay in microsecond granularity.

On many platforms the OS will round the sleep time to millisecond
resolution, but there is no reason for us to pre-emptively round the
argument to pg_usleep.

When the delay was measured in milliseconds and started from 1 ms, it
sometimes took many attempts until the logic that increases the delay by
multiplying with a random value between 1 and 2 actually managed to bump it
from 1 ms to 2 ms. That lead to a sequence of 1 ms waits until the delay
started to increase. This wasn't really a problem but it looked odd if you
observed the waits. There is no measurable difference in performance, but
it's more readable this way.

Jeff Janes
Define Trap and TrapMacro even in non-cassert builds.

In some cases, the use of these macros may be preferable to Assert()
or AssertMacro(), since this way the caller can set the trap message.

Andres Freund and Robert Haas
Make the OVER keyword unreserved.

This results in a slightly less specific error message when OVER
is used in a context where we don't accept window functions, but
per discussion, it's worth it to get the benefit of not needing
to reserve this keyword any more.  This same refactoring will
also let us avoid reserving some other keywords that we expect
to add in upcoming patches (specifically, IGNORE, RESPECT, and
FILTER).

Troels Nielsen, with minor changes by me
pg_upgrade:  change -u to -U, for consistency
Change -u (user) option to -U, for consistency with other tools like
pg_dump and psql.  Also expand --user to --username, again for
consistency.
BACKWARD INCOMPATIBILITY
Send SIGKILL to children if they don't die quickly in immediate shutdown

On immediate shutdown, or during a restart-after-crash sequence,
postmaster used to send SIGQUIT (and then abandon ship if shutdown); but
this is not a good strategy if backends don't die because of that
signal.  (This might happen, for example, if a backend gets tangled
trying to malloc() due to gettext(), as in an example illustrated by
MauMau.)  This causes problems when later trying to restart the server,
because some processes are still attached to the shared memory segment.

Instead of just abandoning such backends to their fates, we now have
postmaster hang around for a little while longer, send a SIGKILL after
some reasonable waiting period, and then exit.  This makes immediate
shutdown more reliable.

There is disagreement on whether it's best for postmaster to exit after
sending SIGKILL, or to stick around until all children have reported
death.  If this controversy is resolved differently than what this patch
implements, it's an easy change to make.

Bug reported by MauMau in message 20DAEA8949EC4E2289C6E8E58560DEC0@maumau

MauMau and Álvaro Herrera
pg_upgrade:  trim down --help and doc option descriptions
Previous code had old/new prefixes on option values, e.g.
--old-datadir=OLDDATADIR.  Remove them, for simplicity;  now:
--old-datadir=DATADIR.  Also update docs to do the same.
pg_upgrade:  remove -h option
-h (help) is not needed;  pg_upgrade already supports --help and -?,
which is consistent with other tools.
pg_upgrade:  pass username to analyze script
If -U (user) is specified, pass the username into the created analyze
script.
Per request from Ray Stell
Assert that ALTER TABLE subcommands have pass set
ALTER TABLE ... ALTER CONSTRAINT for FKs

Allow constraint attributes to be altered,
so the default setting of NOT DEFERRABLE
can be altered to DEFERRABLE and back.

Review by Abhijit Menon-Sen
Change errcode for lock_timeout to match NOWAIT

Set errcode to ERRCODE_LOCK_NOT_AVAILABLE

Zoltán Bsöszörményi
Inline ginCompareItemPointers function for speed.

ginCompareItemPointers function is called heavily in gin index scans -
inlining it speeds up some kind of queries a lot.
ecpg: Consistently use mm_strdup()

mm_strdup() is provided to check errors from strdup(), but some places
were failing to use it.
Fix cpluspluscheck in checksum code

C++ is more picky about comparing signed and unsigned integers.
Retry short writes when flushing WAL.

We don't normally bother retrying when the number of bytes written by
write() is short of what was requested. It is generally assumed that a
write() to disk doesn't return short, unless you run out of disk space.
While writing the WAL, however, it seems prudent to try a bit harder,
because a failure leads to PANIC. The write() is also much larger than most
write()s in the backend (up to wal_buffers), so there's more room for
surprises.

Also retry on EINTR. All signals used in the backend are flagged SA_RESTART
nowadays, so it shouldn't happen, but better to be defensive.
Optimize pglz compressor for small inputs.

The pglz compressor has a significant startup cost, because it has to
initialize to zeros the history-tracking hash table. On a 64-bit system, the
hash table was 64kB in size. While clearing memory is pretty fast, for very
short inputs the relative cost of that was quite large.

This patch alleviates that in two ways. First, instead of storing pointers
in the hash table, store 16-bit indexes into the hist_entries array. That
slashes the size of the hash table to 1/2 or 1/4 of the original, depending
on the pointer width. Secondly, adjust the size of the hash table based on
input size. For very small inputs, you don't need a large hash table to
avoid collisions.

Review by Amit Kapila.
Remove undocumented -h (help) option
The -h option was not supported by many tools, and not documented, so
remove them for consistency from pg_upgrade, pg_test_fsync, and
pg_test_timing.
Update LSB URL in pg_ctl
Update Linux Standard Base Core Specification 3.1 URL mention in pg_ctl
comments.
Improve support for building PGXS modules with VPATH.

A VPATH build will be performed when the module's make file path is not
the current directory or when USE_VPATH is set.

This will assist packagers and others who prefer to build without
polluting the source directories.

There is still a bit of work to do here, notably documentation, but it's
probably a good idea to commit what we have so far and let people test
it out on their modules.

Cédric Villemain, with an addition from me.
Add timezone offset output option to to_char()
Add ability for to_char() to output the timezone's UTC offset (OF).  We
already have the ability to return the timezone abbeviation (TZ/tz).
Per request from Andrew Dunstan