pgsql: Add pg_amcheck, a CLI for contrib/amcheck.

Add pg_amcheck, a CLI for contrib/amcheck.

This makes it a lot easier to run the corruption checks that are
implemented by contrib/amcheck against lots of relations and get
the result in an easily understandable format. It has a wide variety
of options for choosing which relations to check and which checks
to perform, and it can run checks in parallel if you want.

Mark Dilger, reviewed by Peter Geoghegan and by me.

Discussion: http://postgr.es/m/12ED3DA8-25F0-4B68-937D-D907CFBF08E7@enterprisedb.com
Discussion: http://postgr.es/m/BA592F2D-F928-46FF-9516-2B827F067F57@enterprisedb.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/9706092839db2c8c93860674e426a917635438c3

Modified Files
--------------
doc/src/sgml/ref/allfiles.sgml | 1 +
doc/src/sgml/ref/pg_amcheck.sgml | 609 ++++++++
doc/src/sgml/reference.sgml | 1 +
src/bin/Makefile | 1 +
src/bin/pg_amcheck/.gitignore | 3 +
src/bin/pg_amcheck/Makefile | 51 +
src/bin/pg_amcheck/pg_amcheck.c | 2136 ++++++++++++++++++++++++++++
src/bin/pg_amcheck/t/001_basic.pl | 9 +
src/bin/pg_amcheck/t/002_nonesuch.pl | 248 ++++
src/bin/pg_amcheck/t/003_check.pl | 504 +++++++
src/bin/pg_amcheck/t/004_verify_heapam.pl | 516 +++++++
src/bin/pg_amcheck/t/005_opclass_damage.pl | 54 +
src/tools/msvc/Install.pm | 12 +-
src/tools/msvc/Mkvcbuild.pm | 7 +-
14 files changed, 4143 insertions(+), 9 deletions(-)