Avoid deadlocks during insertion into SP-GiST indexes.

SP-GiST's original scheme for avoiding deadlocks during concurrent index
insertions doesn't work, as per report from Hailong Li, and there isn't any
evident way to make it work completely.  We could possibly lock individual
inner tuples instead of their whole pages, but preliminary experimentation
suggests that the performance penalty would be huge.  Instead, if we fail
to get a buffer lock while descending the tree, just restart the tree
descent altogether.  We keep the old tuple positioning rules, though, in
hopes of reducing the number of cases where this can happen.

Teodor Sigaev, somewhat edited by Tom Lane
Fix pg_restore -l with the directory archive to display the correct format name.

Back-patch to 9.1 where the directory archive was introduced.
Fix docs on lock level for ALTER TABLE VALIDATE

ALTER TABLE .. VALIDATE CONSTRAINT previously
gave incorrect details about lock levels and
therefore incomplete reasons to use the option.

Initial bug report and fix from Marko Tiikkaja
Reworded by me to include comments by Kevin Grittner
Fix the create_index regression test for Danish collation.

In Danish collations, there are letter combinations which sort
higher than 'Z'.  A test for values > 'WA' was picking up rows
where the value started with 'AA', causing the test to fail.

Backpatch to 9.2, where the failing test was added.

Per report from Svenne Krap and analysis by Jeff Janes
Further update CREATE FUNCTION documentation about argument names

More languages than SQL and PL/pgSQL actually support parameter names.