[raster] Implementation of ST_AsBinary for RASTER type

[mloskot]

This is just a record of the plan I've made to start implementing ST_AsBinary function for WKT Raster. The function is listed in the big plan.

The first version of [ST_AsBinary I'm going to implement will do nearly the same what ST_byte function does. It's prototype is:

bytea ST_AsBinary(raster r1);

At the moment, I don't aim to implement compression support, but later it can be extended to provide it:

bytea ST_AsBinary(raster r1, text compression);

I haven't planned to handle endianness as PostGIS'  ST_AsBinary does. So, it is expected that WKB is returned with  endianness native to the machine running the PostgreSQL database - it can vary (i.e. Intel returns NDR, PowerPC returns XDR). Feel free to share your suggestions of solutions fot this.

[mloskot]

First version available from the spike (r4346)

[pracine]

This function should return the WKB format of the raster like does the PostGIS ST_AsBinary function.

 http://postgis.refractions.net/documentation/manual-1.4/ST_AsBinary.html

[jorgearevalo]

Functions implemented: - st_asbinary (rtpostgis.sql) --> RASTER_to_binary (rt_pg.c) --> rt_raster_to_wkb (rt_api.c)