Bundle pg_reorg as an extension

[dvarrazzo]

Allows using CREATE EXTENSION on pg_reorg.

State-of-the-art is in the extension branch in this repos. I've originally thought the feature was to be released in 1.2 but for Sakamoto it's ok to have it in 1.1.8

http://pgfoundry.org/pipermail/reorg-general/2012-September/000087.html

[dvarrazzo]

Sakamoto-san was to duplicate pg_reorg.sql with small variations to create the --1.0 script. I don't think it is an easy to maintain solution: I'll add some Makefile + sed gymnastic to create both the files from a single .sql.in.

Also, I've noticed the consensus is to avoid to handle the case of USE_PGXS not set as in an in-tree contrib (e.g. see this article). I'd simplify the Makefile but that's probably better done in master and not in 1.1.x.

[dvarrazzo]

I've merged the extension branch back to maint 1.1.

A few other changes to clean up releasing an extension will be done for 1.2 (e.g. for PG>=9.1 we can release only the extension sql scripts, not the "legacy" ones)