Make functions support named argument call syntax

[robe]

I have started to do this with the raster functions by making sure the function names given match the documented ones.

Now that both PostgreSQL 9.0 and 9.1 support named function arguments I can only assume peopel will begin to think the argument names we have documented in the manual can be used with this syntax. Of course in most cases they can not since many of our functions except for the raster ones even use names.

By named argument call syntax I mean this

SELECT ST_AddBand(rast:= myrast, pixeltype:='8BUI'); 

[robe]

Milestone renamed