[postgis-users] schema support patch 2

[strk]

This is a big change, please give it a try.

AddGeometryColumn AND DropGeometryColumn have been 
moved from 'common' to 'version-specific' enabler scripts.

For versions prior 7.3 schema argument is just discarder.
For versions 7.3 and 7.4 schema argument is checked for existance
and set to current_schema() if empty or invalid (raising a notice
in the latter case).

fix_geometry_columns(), called at the end of every addgeometrycolumn()
call, will set to 'empty' every invalid f_table_schema, with no notice.
DropGeometryColumn will not find any record with an empty f_table_schema,
so people will need to store a valid schema name in the geometry_columns
table if they want to be able to use dropgeometrycolumn.

NOTE: shp2pgsql has not been patched yet, so it will continue to
	produce AddGeometryColumn calls with 'invalid' schema_name.
	(handled by the procedure).

--strk;