Use system semaphore to synchronize with client about rendering buffer access

Open-webOS-DCO-1.0-Signed-off-by: Simon Busch <morphis@gravedo.de>
Implement a remote texture cache to store buffer to texture mappings

Open-webOS-DCO-1.0-Signed-off-by: Simon Busch <morphis@gravedo.de>
Open-webOS-DCO-1.0-Signed-off-by: Florian Haenel <florian.hanel@palm.com>
Hold the last rendered buffer

Signed-off-by: Simon Busch <morphis@gravedo.de>
Make a HostWindow not visible from the beginning

Signed-off-by: Simon Busch <morphis@gravedo.de>