Re: Support for REINDEX CONCURRENTLY

I have been working on improving the code of the 2 patches:
1) reltoastidxid removal:
- Improvement of mechanism in tuptoaster.c to fetch the first valid index
for toast value deletion and fetch
- Added a macro called RelationGetIndexListIfValid that avoids recompiling
the index list with list_copy as RelationGetIndexList does. Not using a
macro resulted in increased shared memory usage when multiple toast values
were added inside the same query (stuff like "insert into tab values
(generate_series(1,1000), '2k_long_text')")
- Fix a bug with pg_dump and binary upgrade. One valid index is necessary
for a given toast relation.
2) reindex concurrently:
- correction of some comments
- fix for index_concurrent_set_dead where process did not wait that other
backends released lock on parent relation
- addition of a error message in index_concurrent_drop if it is tried to
drop a live index. Dropping a live index with only ShareUpdate lock is
dangerous

I am also planning to test the potential performance impact of the patch
removing reltoastidxid with scripts of the type attached. I don't really
know if it can be quantified but I'll give a try with some methods (not yet
completely defined).
-- 
Michael