[raster] ST_Touches in raster and vector space

[dustymugs]

This would be implemented using the underlying C function rt_raster_surface().

[pramsey]

And WTF is rt_raster_surface (and note our love of CamelCase over under_scores).

[dustymugs]

rt_raster_surface creates a multipolygon of the actual area of a raster's band (excludes NODATA pixels).

Functions in rt_pg/* are in camel case while those functions in rt_core/* are not. I've been following the pattern that was in use when I showed up.

[dustymugs]

Like the geometry ST_Touches, the raster ST_Touches will use a spatial index (&& operator) if available.

Raster/Raster variants

1. st_touches(
	rast1 raster, nband1 integer,
	rast2 raster, nband2 integer
) -> boolean

2. st_touches(
	rast1 raster,
	rast2 raster
) -> boolean

Raster/Geometry variants in raster-space

3. st_touches(
	rast raster,
	geom geomtry,
	nband integer DEFAULT NULL
) -> boolean

4. st_touches(
	rast raster,
	nband integer,
	geom geometry
) -> boolean

Geometry/Raster variant in vector-space

5. st_touches(
	geom geometry,
	rast raster,
	nband integer DEFAULT NULL
) -> boolean

[dustymugs]

Added in r10078