Add a filed to PageHeaderData

Dear Hackers

I wanted to add a char array with length of 20 to PageHeaderData in
include/storage/bufpage.h.
Surprisingly regression test failed on rangetypes test!

The diff of resulted and expected file is :

*** 968,974 ****
select count(*) from test_range_spgist where ir -|- int4range(100,500);
count
-------
! 5
(1 row)

-- now check same queries using a bulk-loaded index
--- 968,974 ----
select count(*) from test_range_spgist where ir -|- int4range(100,500);
count
-------
! 2
(1 row)

-- now check same queries using a bulk-loaded index

======================================================================

Any help appreciated.

Soroosh Sardari