Add an install from unpackaged test

[robe]

As part of our extension testing, I propose we add a install from unpackaged.

The general steps would be:

1. count the objects /etc as we do in regular install test
2. Install postgis with postgis.sql/rtpostgis.sql.spatial_ref.sql
3. Count the objects as we do
4. CREATE EXTENSION postgis FROM unpackaged;
5. DROP EXTENSION postgis;
6. count objects

Verifiy that count in 1 and count in 6 are the same.

For 2.2 I plan to do this manually but would be nice to have it wrapped as a test.

[strk]

It could be a special handling for "unpackaged" as a "from" version in the —upgrade-path switch of run_test.pl. Right now using that label fails, anyway:

./run_test.pl -v --extension --upgrade-path unpackaged--2.2.0dev tickets.sql
...
ERROR:  could not stat file "/home/postgresql-9.3.4/share/extension/postgis--unpackaged.sql": No such file or directory

Note this would still require installing the code first.

[strk]

Actually, I'm thinking there might be a problem with using —upgrade-path in that the "unpackaged" label for the "from" component would not be able to express _which_ version of unpackaged to load from. Should maybe be "unpackaged:version" or something like that. Besides, the CREATE EXTENSION command itself doesn't distinguish between versions of "unpackaged", which may be a source of confusion already (think someone creating extension postgis version 2.2.0 from unpackaged version 1.5.0…)

[strk]

Well I've implemented the "unpackaged" support as the from component, let's see where it takes us. It's in r14119.

[strk]

NOTE: —upgrade-path is new in 2.2.0, as per #2652, so this does not need a new NEWS item