pgsql: Fix pgstattuple functions to use regclass-type as the argument.

Fix pgstattuple functions to use regclass-type as the argument.

This allows us to specify the target relation with several expressions,
'relname', 'schemaname.relname' and OID in all pgstattuple functions.
pgstatindex() and pg_relpages() could not accept OID as the argument
so far.

Per discussion on -hackers, we decided to keep two types of interfaces,
with regclass-type and TEXT-type argument, for each pgstattuple
function because of the backward-compatibility issue. The functions
which have TEXT-type argument will be deprecated in the future release.

Patch by Satoshi Nagayasu, reviewed by Rushabh Lathia and Fujii Masao.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/1dc118660b8f12d3bdec94b6f6e1068966ca62e9

Modified Files
--------------
contrib/pgstattuple/Makefile                  |    2 +-
contrib/pgstattuple/expected/pgstattuple.out  |   84 +++++++++++++++++++++++++
contrib/pgstattuple/pgstatindex.c             |   72 +++++++++++++++++++--
contrib/pgstattuple/pgstattuple--1.1--1.2.sql |   39 ++++++++++++
contrib/pgstattuple/pgstattuple--1.1.sql      |   58 -----------------
contrib/pgstattuple/pgstattuple--1.2.sql      |   79 +++++++++++++++++++++++
contrib/pgstattuple/pgstattuple.control       |    2 +-
contrib/pgstattuple/sql/pgstattuple.sql       |   14 +++++
doc/src/sgml/pgstattuple.sgml                 |   47 +++++++++++---
9 files changed, 324 insertions(+), 73 deletions(-)