Until now, Genode's framebuffer session interface was based on the
RGB565 pixel format. This patch changes the pixel format to 32-bit
XRGB where the X part is ignored. It adapts all graphical applications
and device drivers accordingly.
The patch also adjusts the users of the drivers_interactive packages,
assigning 64 MiB RAM and 1500 caps to the drivers subsystem, which is
sufficient for covering high resolutions at 32 bits per pixel and to
accommodate multi-component USB HID input stacks.
Fixes#3784
The headers 'texture_rgb565.h' and 'texture_rgb888' contain
template specializations needed for using the 'Texture::rgba' function
for the respective pixel formats. The specializations were formerly
contained in application-local code.
