v0.55

Sabine 0.55

• Render the runtime probe with SwiftShader on Linux
• Fix Sabine apps on Linux whose window never appeared when Chromium couldn't hand the page over in GPU frames, such as when it couldn't allocate the buffers it shares them in or painted without the GPU. The window kept waiting for GPU frames: it starts its own graphics device only once the compositor shows the first of them directly, and software frames need that device. When Chromium paints without the GPU, or the loaded page still has no GPU frame 2 seconds later, the window now starts its device and shows the page in software frames.
• Fix Sabine apps on Linux with AMD graphics never getting GPU frames. Mesa laid the buffers Chromium hands each frame over in out with delta color compression, which Chromium couldn't use, so no frame reached the window. Sabine's Chromium now runs with AMD_DEBUG=nodcc, added to whatever AMD_DEBUG the app was started with.
• The runtime check that runs when Sabine installs or updates Chromium renders its test page with SwiftShader on Linux. From CEF 156, Chromium renders nothing when its GPU process can't start, as on machines without a display, so the check failed and a working runtime was set aside.