[raster] Addband regresssion test fail on some systems.

[pracine]

Because casting of float to int produce undefined behaviour.

We must explicitly clamp the value instead of just casting it. See discussion at:

​http://postgis.refractions.net/pipermail/postgis-devel/2011-January/011354.html

[mloskot]

To summarise recent discussions, my last proposal was to use ​clamping functions, Pierre followed with ​question about truncating and ​I responded (a bit out of thread but with same subject).

IMO, it is not low priority but at least medium. I think we should decide what to do?

[pracine]

We should implement something like what you proposed.

[pracine]

Do we need to do that only for double_to_16_bit conversion or it is necessary for 32 bit and 8 bit as well?

[pracine]

Fixed in r6920.

Please "make post-install-check" so I can close this one

[jorgearevalo]

post-install-check executed and correct. I close this ticket (open if needed)