Fix pgstatindex using for large indexes

Hi.

In pgstatindex.c and pgstattuple.sql, some variables are defined with
int type. So when we try to get informations about a large index by using
pgstatindex, we get strange value of size and density.
Because the values exceed int-max.
# Like following output. I used pgstatindex just after data load.
So "density" is should be nearly 90.

test=# SELECT * FROM pgstatindex('large_index');
-[ RECORD 1 ]------+------------
version | 2
tree_level | 4
index_size | -1349410816 ★
root_block_no | 119666
internal_pages | 28936
leaf_pages | 1379204
empty_pages | 0
deleted_pages | 0
avg_leaf_density | 60.33 ★
leaf_fragmentation | 0

I think that max_avail and free_space should be uint64.
And the output format for index_size should be "%lld" (INT64_FORMAT).

I made the patch and tryed it. (And it seemed OK.)

test=# SELECT * FROM pgstatindex('large_index');
-[ RECORD 1 ]------+------------
version | 2
tree_level | 4
index_size | 11535491072
root_block_no | 119666
internal_pages | 28936
leaf_pages | 1379204
empty_pages | 0
deleted_pages | 0
avg_leaf_density | 90.64
leaf_fragmentation | 0

I also fix *_pages variables just in case.
Please confirm this.

Best regards.

--
NTT OSS Center
Tatsuhito Kasahara

kasahara.tatsuhito _at_ oss.ntt.co.jp