Update PostGIS provider to support PostGIS 2.0

[RockyLiu]

In the 'postgis.sql' of some previous PostGIS versions(e.g. 1.2~1.4), names of some functions are proposed to change. New equivalent functions with better names are added, and old functions are still maintained. For example, in the 'postgis.sql' of version 1.5:

postgis.sql (version 1.5)

---

-- Deprecation in 1.2.3

CREATE OR REPLACE FUNCTION intersects(geometry,geometry)

RETURNS boolean AS '$libdir/postgis-1.5' LANGUAGE 'C' IMMUTABLE STRICT;

-- PostGIS equivalent function: intersects(geometry,geometry)

CREATE OR REPLACE FUNCTION _ST_Intersects(geometry,geometry)

RETURNS boolean AS '$libdir/postgis-1.5','intersects' LANGUAGE 'C' IMMUTABLE STRICT

---

In PostGIS 2.0, most of the old deprecatory functions are removed(in above example, only _ST_intersects is avail in 2.0). But the PostGIS provider still use these old functions to setup the SQL filter.

So, we should modify file: 'FdoRdbmsPostGisFilterProcessor.cpp' to use new functions if the version of PostGIS is 2.0 or later.

The modification have been finished locally and will be submit if the review is passed.