make world so postgresql extensions are installed

The default install only installs the pgpsql extension. You need to `make world` for the other extensions in contrib to be installed.

These are mostly SQL files, so shouldn't be much of a problem wrt file size.

Hey, it could happen.

[![MCWORLD!!!!](http://dl.dropboxusercontent.com/s/m09hx4x7nkkbnt1/2014-10-17%20at%2011.12%20PM.png)](http://www.youtube.com/watch?v=z8h7J1XIc0E#t=15)