[raster] ST_AsPNG does not support 2BUI. Potential regression

[robe]

I'm not 100% sure, but I think when I created the 2BUI example way back in 2.0, it worked

​http://postgis.net/docs/manual-2.1/RT_ST_AsRaster.html

I try with 2.1.3 and it says raster has to be '8BUI'.

Not a big deal I guess I can just correct the docs, I just wasn't sure if it should be flagged as a regression change. I don't have 2.0 setup at moment to test. I suppose it could be GDAL specific too since I was testing with 1.8 back then.

[robe]

I'm just going to change the doc example to take out the 2BUI. May very well have never worked and it was a typo in docs all along and I'm not going to bother backporting the doc change to 2.2 or 2.3

[robe]

In 16503:

Fix crasher in raster when fed an empty raster (note was tempted to change the def of empty raster to include raster with no bands but not sure where else that is used, so just revised the clip check to not try to clip if no bands).
References #3055 for PostGIS 2.5 (trunk),
also minor doc fix references #2925 for PostGIS 2.5 (trunk)

[robe]

In 16504:

Fix crasher in raster when fed an empty raster (note was tempted to change the def of empty raster to include raster with no bands but not sure where else that is used, so just revised the clip check to not try to clip if no bands).
References #3055 for PostGIS 2.4.4,
also minor doc fix references #2925 for PostGIS 2.4.4

[robe]

In 16505:

Fix crasher in raster when fed an empty raster (note was tempted to change the def of empty raster to include raster with no bands but not sure where else that is used, so just revised the clip check to not try to clip if no bands).
References #3055 for PostGIS 2.3.7,
also minor doc fix references #2925 for PostGIS 2.3.7
reorder NEWS tickets numerically