v0.5.0

This release brings with it greatly improved support for HDR (including
HDR-in-SDR emulation, native HDR passthrough and improvements to the
HDR->SDR tone mapping algorithm), as well as support for ICC profiles
and external VkImage interop (needed for e.g. hardware decoding).

Additions:
- Add support for treating an SDR curve as an HDR curve by
  overriding/providing the true target peak. This essentially allows you
  to calibrate a true HDR device to a typical SDR curve and use it to
  display HDR media, at the cost of bit precision
- Add more values to enum pl_chroma_location
- Add a scale factor to struct pl_sample_src, which is useful for e.g.
  debanding on bit-shifted inputs
- Add a new function to infer/guess unknown pl_color_space fields
- Add support for 3DLUTs / ICC profiles (via LittleCMS), including
  support for assigning ICC profiles to the `pl_render_image` and
  `pl_render_target` structs
- Allow enabling optional extra vulkan device/instance extensions, as
  well as listing what extensions were actually loaded
- Add an API for VkImage interop with user code, e.g. to wrap mapped
  hardware decoding planes into `pl_tex`, plus all synchronization code
  and extra metadata necessary to make this interop safe
- Implement support for native HDR output on supported platforms

Changes:
- Separate the texture from the plane data struct in `pl_upload_plane`
- Swapchain FBOs are now guaranteed to be blittable (e.g. pl_tex_clear)
- Tone mapping is no longer done for desaturation steps. Users wanting
  high quality desaturation should use ICC profiles
- Change the types of various fields in struct pl_gpu_limits
- Slightly relax the sizing requirements of pl_tex_transfer
- Change the default value for pl_tex_transfer_params.stride_w/h.
  Instead of defaulting to the image size, they now default to the rect to
  be transferred
- Texture transfer buffer offsets must (now) be aligned to the texel
  size, in addition to being a multiple of 4
- Change the API of `pl_color_space_equal` to be consistent with the
  rest of the colorspace APIs
- Allow the `pl_upload_plane` helpers to upload from buffers as well
- Switch the type of mapped buffer pointers from char* to uint8_t*
- Rename DCI_P3 to Display_P3, and add DCI_P3 (using the actual DCI white
  point)

Fixes and performance improvements:
- Fix some compatibility issues with GLSL 120
- Prevent desaturation from exploding when tone mapping to HDR, or when
  tone mapping a very bright HDR scene to SDR
- Implement the fully parametrized BT.2100 (HLG) OOTF in both
  directions, based on the tagged/inferred signal peak
- Fix an issue preventing the out-of-gamut feature from working
  correctly on HDR displays
- Fix a segfault that occurs when instance creation fails
- Fix an issue where `peak_detect_frames` was sometimes too low
- Allow debanding to take care of implicit bilinear sampling in cases
  where no other scaler is requested, thus avoiding an unnecessary FBO
  indirection
- Only run the debanding algorithm on the parts of the image we will
  actually be displaying. This is relevant when cropping
- Fix an issue where PL_TONE_MAPPINg_MOBIUS could fail in certain
  (unrealistic) scenarios involving HDR-in-SDR emulation
- Fix an issue where vulkan could sometimes modify commands after
  submitting them, when recreating vertex buffers
- Make an effort to reuse the same vertex buffer when the contents don't
  change from the previous invocation
- Fix the glslang locale work-arounds on windows
- Fix an issue where trying to upload from a too-large texel buffer
  results in an assertion failure rather than a clean error
- Fix an issue where the usage of VkEvents prevented libplacebo from
  working on platforms where they were unsupported (e.g. MoltenVK)
- Support and use vulkan push descriptors where supported. This avoids
  having to maintain, update and synchronize descriptor sets
- Correctly disable signal linearization on low-bit depth FBOs
- Prevent a crash on the (pathological) case of a shader with no
  descriptors
- Fix a bug in the size limit calculations for 2D/3D LUTs
- Use optimization level "performance" instead of "size" for shader
  compilation
- Fix an abort() when trying to render to a non-storable FBO when using
  a final pass that requires compute shaders (e.g. HDR peak detection)
This tag has no release notes.