release version 0.5.0

- ABI Changes:
    - PrepareCallback return type change in Player.prepare()
    - Player.snapshot() callback return type change. Return a file path to save as file(not implemented yet)
    - Add SeekFlag for prepare(), setNextMedia() and gaplessSwitch()
- APIs Changes:
    - Add RenderAPI.h: provides necessary informations to use a graphics api other than OpenGL
    - Add Player.setRenderAPI(): select platform graphics api for video rendering. Now OpenGL(default) and D3D11 are supported.
    - Add version macros
- New Features:
    - Experimental D3D11 rendering support. Now can render frames from software decoders. Color is not precise as OpenGL. Only the context created internally from a HWND via updateNativeSurface is tested. Foreign contexts may work, not tested.
- Improve seeking performance, fix unchanged display when seeking continuously. Now it's close to mpv, and should be better than most players like potplayer, vlc, mpc-hc etc.
- Fix seek position if media start time > 0
- Accurate seek is the default for the start position of prepare(), setNextMedia() and gaplessSwitch()
- OpenGL: Skip uploading video frame to gpu when redrawing
- setState(State::Stopped) now clears video renderer viewport and releases video renderer resources
- Fix stopping playback is not executed immediately
- setState(State::Stopped) now releases host and gpu resouces and clear background color. Normal playback end does not, and still keep the last frame displayed
- Fix setState() sometimes does not work
- MFT Decoder:
    - Disable low latency by default only for hevc. Previous release turned off low latency mode for all codecs, then h264 decoding may be too slow
    - Add property "ignore_profile" and "ignore_level"
- Add FFmpeg decoder property "drop" to control decoder frame dropping when seeking
- glfwplay example:
    - new seek options: `-seek_step`, `-seek_any`
    - support d3d11 rendering using `-d3d11 -gfxthread`

Author: wang-bin

README.md

@@ -31,17 +31,7 @@ If ffmpeg any module is not set, it's searched in the following order
 - C++ APIs: a header only thin wrapper for C APIs. No C++ ABI restriction. No user code change to switch between ABI level APIs and C++ APIs.
 
 ## TODO:
-- HDR support
-- [x] windows 10 HDR apis (ANGLE GLES2/3)
-- [x] color primaries convertion
-- [x] tone mapping
-- [ ] hdr device
-- Encoding, transcoding and streaming
-- Subtitle decoder and renderer
-- Vulkan
-- D3D
-- Metal
-- V4L2 codecs + 0-copy rendering(Raspberry pi)
+https://github.com/wang-bin/mdk-sdk/wiki/TODO
 
 ## Open Source Modules and Examples
 - MFT decoder module: https://github.com/wang-bin/mdk-mft