pgsql: Add: > > * Add REINDEX CONCURRENTLY, like CREATE INDEX

Log Message:
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Add:

* Add REINDEX CONCURRENTLY, like CREATE INDEX CONCURRENTLY

This is difficult because you must upgrade to an exclusive table lock
to replace the existing index file. CREATE INDEX CONCURRENTLY does not
have this complication. This would allow index compaction without
downtime.

Modified Files:
--------------
pgsql/doc:
TODO (r1.2057 -> r1.2058)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.2057&r2=1.2058)
pgsql/doc/src/FAQ:
TODO.html (r1.558 -> r1.559)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.558&r2=1.559)