[raster] ST_MapAlgebra raster/scripts/plpgsql some broken

[robe]

-- this is invalid (that should be $4 I believe)

CREATE OR REPLACE FUNCTION ST_MapAlgebra(rast raster, band integer, expression text, nodatavalexpr text) 
    RETURNS raster
    AS 'SELECT ST_MapAlgebra($1, $2, $3, nodatavalexpr, NULL)'
    LANGUAGE 'SQL' IMMUTABLE;

--- this is invalid (it might be because I'm testing on 9.1 (though 9.0 should have the same issue) since both support named variables function call syntax and so are more stringent about naming -

CREATE OR REPLACE FUNCTION ST_MapAlgebra(rast raster, expression text, nodatavalexpr text) 
    RETURNS raster
    AS 'SELECT ST_MapAlgebra($1, 1, $2, $3, NULL)'
    LANGUAGE 'SQL' IMMUTABLE;

gives error

ERROR: cannot change name of input parameter "pixeltype" HINT: Use DROP FUNCTION first.

[robe]

To add to this -- this function also makes use of

ST_HasNoBand(rast, band) 

ERROR:  function st_hasnoband(raster, integer) does not exist
LINE 1: SELECT ST_HasNoBand(rast, band)

Can't we just replace this with is ST_NumBands(rast) < band

[dzwarg]

Attached are fixes that repair the prototype st_mapalgebra.sql file in the scripts/plpgsql folder.

[pracine]

Fixed in r7659 by removing all the variants. They are not necessary in the prototype.