Patch for collation using ICU

Hi!

I've put together a patch for using IBM's ICU package for collation.

If your OS does not have full support for collation ur uppercase/lowercase
in multibyte locales, this might be useful. If you are using a multibyte
character encoding in your database and want collation, i.e. order by, and
also lower(), upper() and initcap() to work properly, this patch will do
just that.

This patch is needed for FreeBSD, since this OS has no support for
collation of for example unicode locales (that is, wcscoll(3) does not do
what you expect if you set LC_ALL=sv_SE.UTF-8, for example). AFAIK the
patch is *not* necessary for Linux, although IBM claims ICU collation to be
about twice as fast as glibc for simple western locales.

It adds a configure switch, `--with-icu', which will set up the code to use
ICU instead of wchar_t and wcscoll.

This has been tested only on FreeBSD-4.11 & FreeBSD-5-stable, where it
seems to run well. I've not had the time to do any comparative performance
tests yet, but it seems it is at least not slower than using LATIN1 with
sv_SE.ISO8859-1 locale, perhaps even faster.

I'd be delighted if some more experienced postgresql hackers would review
this stuff. The patch is pretty compact, so it's fast reading :) I'm
planning to add this patch as an option (tagged "experimental") to
FreeBSD's postgresql port. Any ideas about whether this is a good idea or
not?

Any thoughts or ideas are welcome!

Cheers,
Palle

Patch at:
<http://people.freebsd.org/~girgen/postgresql-icu/pg-801-icu-2005-03-14.diff>

ICU at sourceforge: <http://icu.sf.net/>