pgsql: Improve BRIN infra, minmax opclass and regression test

Improve BRIN infra, minmax opclass and regression test

The minmax opclass was using the wrong support functions when
cross-datatypes queries were run.  Instead of trying to fix the
pg_amproc definitions (which apparently is not possible), use the
already correct pg_amop entries instead.  This requires jumping through
more hoops (read: extra syscache lookups) to obtain the underlying
functions to execute, but it is necessary for correctness.

Author: Emre Hasegeli, tweaked by Álvaro
Review: Andreas Karlsson

Also change BrinOpcInfo to record each stored type's typecache entry
instead of just the OID.  Turns out that the full type cache is
necessary in brin_deform_tuple: the original code used the indexed
type's byval and typlen properties to extract the stored tuple, which is
correct in Minmax; but in other implementations that want to store
something different, that's wrong.  The realization that this is a bug
comes from Emre also, but I did not use his patch.

I also adopted Emre's regression test code (with smallish changes),
which is more complete.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/db5f98ab4fa44bc563ec62d7b1aada4fc276d9b2

Modified Files
--------------
contrib/pageinspect/brinfuncs.c       |    2 +-
doc/src/sgml/brin.sgml                |    4 +-
src/backend/access/brin/brin_minmax.c |  154 +++++++++++++++-----------
src/backend/access/brin/brin_tuple.c  |    6 +-
src/include/access/brin_internal.h    |    7 +-
src/include/catalog/catversion.h      |    2 +-
src/include/catalog/pg_amproc.h       |  164 ----------------------------
src/include/catalog/pg_opclass.h      |   54 +++++-----
src/test/regress/expected/brin.out    |  188 ++++++++++++++++++++------------
src/test/regress/sql/brin.sql         |  192 +++++++++++++++++++++------------
10 files changed, 369 insertions(+), 404 deletions(-)