Construct ctid string correctly for block no > 2^31.
Construct ctid string correctly for block no > 2^31.

Block number is unsigned. Other places where we construct ctid strings we
got this right, but not this one. I'm not sure how to trigger this codepath,
but I'm sure something funny would happen if you tried to use these functions
on large enough tables (> 16 TB).

treasure-data/prestogres-odbc,hlinnaka/psqlodbc,gavioto/psqlodbc,gavioto/psqlodbc,treasure-data/prestogres-odbc,hlinnaka/psqlodbc,hlinnaka/psqlodbc,treasure-data/prestogres-odbc,gavioto/psqlodbc