Make PostgreSQL 9.0 the official minimum

[robe]

I think we all agreed there is not much benefit to supporting 8.4 on 2.1. I think strk is the only one still running 8.4 against trunk (and he has already raised his white flag :) ).

strk -- as the last hold out -- when you are ready, can you enforce the 9.0 requirement. I have already updated the docs at r9960 to reflect the new minimum -- and the matrix was already updated http://trac.osgeo.org/postgis/wiki/UsersWikiPostgreSQLPostGIS . So now we just need to do the hard change.

[strk]

r10235

[pramsey]

Removed now-defunct code at r10281