pgsql: Fix up handling of C/POSIX collations.

Fix up handling of C/POSIX collations.

Install just one instance of the "C" and "POSIX" collations into
pg_collation, rather than one per encoding.  Make these instances exist
and do something useful even in machines without locale_t support: to wit,
it's now possible to force comparisons and case-folding functions to use C
locale in an otherwise non-C database, whether or not the platform has
support for using any additional collations.

Fix up severely broken upper/lower/initcap functions, too: the C/POSIX
fastpath now does what it is supposed to, and non-default collations are
handled correctly in single-byte database encodings.

Merge the two separate collation hashtables that were being maintained in
pg_locale.c, and be more wary of the possibility that we fail partway
through filling a cache entry.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/176d5bae1d636fc1e91840b12cbd04c96d638b7e

Modified Files
--------------
doc/src/sgml/charset.sgml          |  140 ++++++++---
src/backend/utils/adt/formatting.c |  163 ++++++++++--
src/backend/utils/adt/pg_locale.c  |  488 ++++++++++++++++++++----------------
src/bin/initdb/initdb.c            |   18 +-
src/include/catalog/catversion.h   |    2 +-
src/include/catalog/pg_collation.h |   15 +-
src/include/port.h                 |    2 +
src/port/pgstrcasecmp.c            |   26 ++
8 files changed, 572 insertions(+), 282 deletions(-)