The GTK and OS X platforms already ignored the requested bit depth and
always used 32 bit. Windows and SDL would set a 16 bit color depth for
the screen, but still did all of the rendering short of the final
present in 32 bit.
The magic value -1 is used to denote "current screen mode", but it has trouble fitting into the unsigned concept. An alternative would be to use 0 as the magic value, but that would include quite a few places (including existing configuration settings) to change.
In comparison to the old system, this is a downgrade - instead of being
able to set a full color mapping by gamma ramp, we now get just a value
per colour channel.
Upside is that we do not need to play around with the global gamma ramps
any more, which was arguably the wrong way to do it.
This commit will likely break everything that has been using gamma so far.
This makes it possible to ship the bundle stand-alone. Also
note that CMake will automatically pack the game data for
release builds, but sym-link the game data for debug builds.
Note this means you will only see the parts of planet/ that
are mentioned in OC_C4GROUPS in CMakeList.txt! This is equivalent
to the behaviour of the shipped build, so I don't see this as
a problem.