Windows doesn't have M_PI; define it ourselves when needed.

This should fix the Windows build, broken by commit ed802e7d.
pg_upgrade:  remove reference to autovacuum_multixact_freeze_max_age

autovacuum_multixact_freeze_max_age was added as a pg_ctl start
parameter in 9.3.X to prevent autovacuum from running.  However, only
some 9.3.X releases have autovacuum_multixact_freeze_max_age as it was
added in a minor PG 9.3 release.  It also isn't needed because -b turns
off autovacuum in 9.1+.

Without this fix, trying to upgrade from an early 9.3 release to 9.4
would fail.

Report by EDB

Backpatch through 9.3
pg_upgrade:  assume user is install user

The user specified to the upgrade was effectively the install user, but
that was not clearly stated in the comments, documentation, or error
messages.
Improve some JSON error messages.

These messages are new in 9.4, which hasn't been released yet, so
back-patch to REL9_4_STABLE.

Daniele Varrazzo
Fix typo in C comment.
Change ParseConfigFp() so that it doesn't process unused entry of each parameter.

When more than one setting entries of same parameter exist in the
configuration file, PostgreSQL uses only entry appearing last in
configuration file scan. Since the other entries are not used,
ParseConfigFp() doesn't need to process them, but previously it did
that. This problematic behavior caused the configuration file scan
to detect invalid settings of unused entries (e.g., existence of
multiple entries of PGC_POSTMASTER parameter) and log the messages
complaining about them.

This commit changes the configuration file scan so that it processes
only last entry of each parameter.

Note that when multiple entries of same parameter exist both in
postgresql.conf and postgresql.auto.conf, unused entries in
postgresql.conf are still processed only at postmaster startup.

The problem has existed since old version, but a user is more likely
to encounter it since 9.4 where ALTER SYSTEM command was introduced.
So back-patch to 9.4.

Amit Kapila, slightly modified by me. Per report from Christoph Berg.
Refactor pg_receivexlog main loop code, for readability, take 2.

Previously the source codes for processing the received data and handling
the end of stream were included in pg_receivexlog main loop. This commit
splits out them as separate functions. This is useful for improving the
readability of main loop code and making the future pg_receivexlog-related
patch simpler.
Fix alternate regression test output file.

Commit 0ef99bdce3a6cd3195d7df12093042c16328c71c broke this.

Jeff Janes
Don't require sort support functions to provide a comparator.

This could be useful for datatypes like text, where we might want
to optimize for some collations but not others.  However, this patch
doesn't introduce any new sortsupport functions that work this way;
it merely revises the code so that future patches may do so.

Patch by me.  Review by Peter Geoghegan.
Add PG_RETURN_UINT16 macro.

Manuel Kniep
Improve comment.

Based on the old comment, it took me a while to figure out what the
problem was. The importnat detail is that SSL_read() can return WANT_READ
even though some raw data was received from the socket.
pg_upgrade: prevent oid conflicts with new-cluster TOAST tables

Previously, TOAST tables only required in the new cluster could cause
oid conflicts if they were auto-numbered and a later conflicting oid had
to be assigned.

Backpatch through 9.3
Fix typo in docs.

s/XIDs XIDs/XIDs/ in one place in maintenance.sgml.

Guillaume Lelarge
Add -F option to pg_receivexlog, for specifying fsync interval.

This allows us to specify the maximum time to issue fsync to ensure
the received WAL file is safely flushed to disk. Without this,
pg_receivexlog always flushes WAL file only when it's closed and
which can cause WAL data to be lost at the event of a crash.

Furuya Osamu, heavily modified by me.
Small message fixes
Merge remote-tracking branch 'origin/master' into rollups_branch