release version 0.3.1

this is a bug fix release

- fix user stop block
- fix some bugs at eof, e.g. unable to seek
- fix setLoop(0) can not disable looping
- support clang-cl 9.0
- c++ api: support g++ 4.9
- vaapi: sync surface after exporting drm handle
- improve ci. now nightly packages are uploaded automatically to https://sourceforge.net/projects/mdk-sdk/files/nightly
- now mdk can be installed via nuget in visual studio. https://www.nuget.org/packages/mdk

Author: wang-bin

README.md

@@ -7,7 +7,7 @@ Install via [NuGet](https://www.nuget.org/packages/mdk) in Visual Studio
 ## Features
 - Simple and powerful API set
 - Cross platform: Windows, UWP, Linux, macOS, Android, iOS, Raspberry Pi
-- Hardware accelerated decoding and 0-copy GPU rendering for all supported platforms
+- Hardware accelerated decoding and 0-copy GPU rendering for all platforms
 - OpenGL rendering w/ or w/o user provided context
 - Ingegrated with any gui toolkits via OpenGL (Qt, SDL, glfw, SFML etc.) easily
 - Seamless/Gapless media and bitrate switch for any media
@@ -29,7 +29,7 @@ Install via [NuGet](https://www.nuget.org/packages/mdk) in Visual Studio
 - [x] tone mapping
 - [ ] hdr device
 - Encoding, transcoding and streaming
-- Subtitle
+- Subtitle decoder and renderer
 - Vulkan
 - D3D
 - V4L2 codecs + 0-copy rendering(Raspberry pi)