Update function names in loader to ST_

[pramsey]

The shp2pgsql and pgsql2shp infrastructure was written prior to the advent of the ST_ prefix. In order to future proof it against deprecation, the code should use appropriate, standards based ST_ functions where ever possible. This will break backward compatibility against PostGIS versions 1.1 and lower.

[robe]

I did this one already I think when I was purging legacy names.