[raster] ST_DumpAsPolygons() stop differenciate values when they are higher than 1048576

[pracine]

This works fine:

SELECT (ST_DumpAsPolygons(ST_SetValue(ST_AddBand(ST_MakeEmptyRaster(1, 2, 0, 0, 1), '32BUI'::text, 1048575), 1, 1, 1048576))).* rast

returning two polygons, but this fails:

SELECT (ST_DumpAsPolygons(ST_SetValue(ST_AddBand(ST_MakeEmptyRaster(1, 2, 0, 0, 1), '32BUI'::text, 1048576), 1, 1, 1048577))).* rast

The only difference is when the pixel values get over 1048576 (which is 0x100000 by the way).

[pracine]

Might be a symptom of #2353

[robe]

Going to assume this is a GDAL bug. Still a problem with PostGIS 2.5.0beta1 and GDAL 2.2.4. I'll need to check 2.3 to see if it's fixed in GDAL 2.3