If the ICU locale is not specified, initialize the default collator
and retrieve the locale name from that.

Discussion: https://postgr.es/m/510d284759f6e943ce15096167760b2edcb2e700.camel@j-davis.com
Reviewed-by: Peter Eisentraut

Backpatch-through: 11

No headers requiring FRONTED to be defined are included as of af1a949109d.

Since this is the last user of (contrib|frontend)_defines in Mkvcbuild.pm,
remove them.

Discussion: https://postgr.es/m/20220820194550.725755r6fj2ro3rx@awork3.anarazel.de

createdb() didn't check for collation attributes validity, which has
to be done explicitly on ICU < 54.  It also forgot to close the ICU collator
opened during the check which leaks some memory.

To fix both, add a new check_icu_locale() that does all the appropriate
verification and close the ICU collator.

initdb also had some partial check for ICU < 54.  To have consistent error
reporting across major ICU versions, and get rid of the need to include ucol.h,
remove the partial check there.  The backend will report an error if needed
during the post-boostrap iniitialization phase.

Author: Julien Rouhaud <julien.rouhaud@free.fr>
Discussion: https://www.postgresql.org/message-id/20220319041459.qqqiqh335sga5ezj@jrouhaud

This adds the option to use ICU as the default locale provider for
either the whole cluster or a database.  New options for initdb,
createdb, and CREATE DATABASE are used to select this.

Since some (legacy) code still uses the libc locale facilities
directly, we still need to set the libc global locale settings even if
ICU is otherwise selected.  So pg_database now has three
locale-related fields: the existing datcollate and datctype, which are
always set, and a new daticulocale, which is only set if ICU is
selected.  A similar change is made in pg_collation for consistency,
but in that case, only the libc-related fields or the ICU-related
field is set, never both.

Reviewed-by: Julien Rouhaud <rjuju123@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/5e756dd6-0e91-d778-96fd-b1bcb06c161a%402ndquadrant.com

Backpatch-through: 10

Backpatch-through: 9.5

Formerly, various frontend directories symlinked these two sources
and then built them locally.  That's an ancient, ugly hack, and
we now have a much better way: put them into libpgcommon.
So do that.  (The immediate motivation for this is the prospect
of having to introduce still more symlinking if we don't.)

This commit moves these two files absolutely verbatim, for ease of
reviewing the git history.  There's some follow-on work to be done
that will modify them a bit.

Robert Haas, Tom Lane

Discussion: https://postgr.es/m/CA+TgmoYO8oq-iy8E02rD8eX25T-9SmyxKWqqks5OMHxKvGXpXQ@mail.gmail.com

Backpatch-through: update all files in master, backpatch legal files through 9.4

When maintaining or merging patches, one of the most common sources
for conflicts are the list of objects in makefiles. Especially when
the split across lines has been changed on both sides, which is
somewhat common due to attempting to stay below 80 columns, those
conflicts are unnecessarily laborious to resolve.

By splitting, and alphabetically sorting, OBJS style lines into one
object per line, conflicts should be less frequent, and easier to
resolve when they still occur.

Author: Andres Freund
Discussion: https://postgr.es/m/20191029200901.vww4idgcxv74cwes@alap3.anarazel.de