Instead of buffers being both drm framebuffers and gbm / dumb buffers, these
responsibilities are now split, which makes it possible to do zero copy
screen casting in the future.
Both framebuffers and gbm / dumb buffers also now always hold a valid underlying
resource, which simplifies code a bit.
The main motivation behind this change is to unify render target
representation across opengl and software renderers and avoid accessing
the render backend directory in order to get the render target.
The .clang-format file is based on the one in ECM except the following
style options:
- AlwaysBreakBeforeMultilineStrings
- BinPackArguments
- BinPackParameters
- ColumnLimit
- BreakBeforeBraces
- KeepEmptyLinesAtTheStartOfBlocks
