Re: WIP: Fast GiST index build

Hi!

Here is last verion of the patch.
List of changes:
1) Neighbor relocation and prefetch were removed. They will be supplied as
separate patches.
2) Final emptying now using standart lists of all buffers by levels.
3) Automatic switching again use simple comparison of index size and
effective_cache_size.
4) Some renames. In particular GISTLoadedPartItem
to GISTBufferingInsertStack.
5) Some comments were corrected and some were added.
6) pgindent
7) rebased with head

Readme update and user documentation coming soon.

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With best regards,
Alexander Korotkov.