pgsql: Add index-only scan support to btree_gist.

Add index-only scan support to btree_gist.

inet, cidr, and timetz indexes still cannot support index-only scans,
because they don't store the original unmodified value in the index, but a
derived approximate value.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/e09b48316c22fce727bce3c89fa64fc627787e6a

Modified Files
--------------
contrib/btree_gist/Makefile | 3 +-
contrib/btree_gist/btree_cash.c | 8 +
contrib/btree_gist/btree_date.c | 7 +
contrib/btree_gist/btree_float4.c | 8 +
contrib/btree_gist/btree_float8.c | 8 +
contrib/btree_gist/btree_gist--1.0--1.1.sql | 127 +++
contrib/btree_gist/btree_gist--1.0.sql | 1491 -------------------------
contrib/btree_gist/btree_gist--1.1.sql | 1570 +++++++++++++++++++++++++++
contrib/btree_gist/btree_gist.control | 2 +-
contrib/btree_gist/btree_int2.c | 8 +
contrib/btree_gist/btree_int4.c | 8 +
contrib/btree_gist/btree_int8.c | 8 +
contrib/btree_gist/btree_interval.c | 9 +
contrib/btree_gist/btree_macaddr.c | 8 +
contrib/btree_gist/btree_oid.c | 8 +
contrib/btree_gist/btree_time.c | 8 +
contrib/btree_gist/btree_ts.c | 8 +
contrib/btree_gist/btree_utils_num.c | 58 +
contrib/btree_gist/btree_utils_num.h | 1 +
contrib/btree_gist/btree_utils_var.c | 18 +
contrib/btree_gist/expected/bit.out | 10 +
contrib/btree_gist/expected/bytea.out | 17 +
contrib/btree_gist/expected/cash.out | 6 +-
contrib/btree_gist/expected/char.out | 16 +
contrib/btree_gist/expected/char_1.out | 16 +
contrib/btree_gist/expected/date.out | 6 +-
contrib/btree_gist/expected/float4.out | 6 +-
contrib/btree_gist/expected/float8.out | 2 +-
contrib/btree_gist/expected/int2.out | 6 +-
contrib/btree_gist/expected/int4.out | 6 +-
contrib/btree_gist/expected/int8.out | 2 +-
contrib/btree_gist/expected/interval.out | 2 +-
contrib/btree_gist/expected/macaddr.out | 23 +
contrib/btree_gist/expected/numeric.out | 19 +
contrib/btree_gist/expected/text.out | 16 +
contrib/btree_gist/expected/text_1.out | 16 +
contrib/btree_gist/expected/time.out | 2 +-
contrib/btree_gist/expected/timestamp.out | 2 +-
contrib/btree_gist/expected/timestamptz.out | 2 +-
contrib/btree_gist/expected/varbit.out | 10 +
contrib/btree_gist/sql/bit.sql | 5 +
contrib/btree_gist/sql/bytea.sql | 6 +
contrib/btree_gist/sql/char.sql | 6 +
contrib/btree_gist/sql/macaddr.sql | 6 +
contrib/btree_gist/sql/numeric.sql | 6 +
contrib/btree_gist/sql/text.sql | 6 +
contrib/btree_gist/sql/varbit.sql | 5 +
47 files changed, 2077 insertions(+), 1514 deletions(-)