Add pgstattuple2 function to allow block sampling in order to
estimate live tuples, dead tuples and free spaces in the specified
table.
Merge branch 'master' into pgstattuple2
Merge branch 'master' into pgstattuple2
Merge branch 'master' into pgstattuple2
Merge branch 'master' into pgstattuple2
Merge branch 'master' into pgstattuple2

Conflicts:
	contrib/pgstattuple/Makefile
	contrib/pgstattuple/pgstattuple--1.1--1.2.sql
	contrib/pgstattuple/pgstattuple--1.2.sql
Fix to remove a duplicated declaration.
Merge remote branch 'remotes/postgres2/pgstattuple2' into pgstat2