Opengl watermark

this patch adds videolabs wattermarking the the trial

• image are embed in the sources using xxd, generated version is embed in the source for now as I dont' think the docker images have this tool. Right now we have the image in both png and raw (only one is compile) as we don't have an easy way do decode png to RBGA from the client as far as I know

• rework the trial mode, the code is always present but enabled using #define, so we don't need to maintain it as an external patch

disclamer: I haven't test my changes on windows