Re: [HACKERS] [PATCH] Pageinspect - add functions on GIN and GiSTindexes from gevel

the following patch transfers functionality from gevel module
(http://www.sai.msu.su/~megera/wiki/Gevel) which provides functions for
analyzing GIN and GiST indexes to pageinspect. Gevel was originally
designed by Oleg Bartunov, and Teodor Sigaev for developers of GiST and
GIN indexes.

Functions added:
 - gist_stat(text) - shows statistics on GiST Tree
 - gist_tree(text) - shows GiST tree
 - gist_tree(text, int4) - shows GiST tree up to MAXLEVEL
 - gist_print(text) - prints objects stored in GiST tree
 - spgist_stat(text) - shows statistics on SP-GiST
 - spgist_print(text) - prints objects stored in index
 - gin_value_count() - originally gin_stat(text) - prints estimated counts
for index values
 - gin_stats() - originally gin_statpage(text) - shows statistics
 - gin_count_estimate(text, tsquery) - shows number of indexed rows matched
query

Tests also transferred, docs for new functions are added. I run pgindent
over the code, but the result is different from those I expected, so I leave
pgindented one.
The patch is applicable to the commit 866f4a7c210857aa342bf901558d170325094dde.