remove explicitly set postgres/postgis version

Get the version from the database where necessary or simply
probe for existence of features. Fake hstore_to_json when
necessary.

Bumps the minimum required versions fro postgres to 9.1 and
for postgis to 2.0.

sql/functions.sql

@@ -1,3 +1,15 @@
+-- Splits the line at the given point and returns the two parts
+-- in a multilinestring.
+CREATE OR REPLACE FUNCTION split_line_on_node(line GEOMETRY, point GEOMETRY)
+RETURNS GEOMETRY
+  AS $$
+BEGIN
+  RETURN ST_Split(ST_Snap(line, point, 0.0005), point);
+END;
+$$
+LANGUAGE plpgsql;
+
+
 CREATE OR REPLACE FUNCTION geometry_sector(partition INTEGER, place geometry) RETURNS INTEGER
   AS $$
 DECLARE

sql/postgis_15_aux.sql

@@ -1,14 +0,0 @@
--- Splits the line at the given point and returns the two parts
--- in a multilinestring.
-CREATE OR REPLACE FUNCTION split_line_on_node(line GEOMETRY, point GEOMETRY)
-RETURNS GEOMETRY
-  AS $$
-DECLARE
-  frac FLOAT;
-BEGIN
-  frac := ST_Line_Locate_Point(line, point);
-  RETURN ST_Collect(ST_Line_Substring(line, 0, frac),
-         ST_Line_Substring(line, frac, 1));
-END
-$$
-LANGUAGE plpgsql;

sql/postgis_20_aux.sql

@@ -1,10 +0,0 @@
--- Splits the line at the given point and returns the two parts
--- in a multilinestring.
-CREATE OR REPLACE FUNCTION split_line_on_node(line GEOMETRY, point GEOMETRY)
-RETURNS GEOMETRY
-  AS $$
-BEGIN
-  RETURN ST_Split(ST_Snap(line, point, 0.0005), point);
-END;
-$$
-LANGUAGE plpgsql;