Wgpu

Fixed:

* Exceptions in user-interaction callbacks don't break the glfw loop anymore.
* Pointer events in glfw have the correct key modifiers now.

Added:

* 224 - Added `add_event_handler` and `remove_event_handler` to GLFW and Jupyter GUI canvases.

- Major API changes:
- `RenderPipelineDescriptor`
- `BindingType`
- new `ShaderModuleDescriptor`
- new `RenderEncoder`
- Features:
- (beta) WGSL support, including the ability to bypass SPIR-V entirely
- (beta) implicit bind group layout support
- better error messages
- timestamp and pipeline statistics queries
- ETC2 and ASTC compressed textures
- (beta) targeting Wasm with WebGL backend
- reduced dependencies
- Native-only:
- clamp-to-border addressing
- polygon fill modes
- query a format for extra capabilities
- `f64` support in shaders
- Validation:
- shader interface
- render pipeline descriptor
- vertex buffers

Changed:

* Now targeting wgpu-native v0.11.0.1, containing many upstream fixes and improvements.
* The `[[block]]` syntax in shaders has been dropped.
* Renamed `ProgrammableStage.clamp_depth` -> `unclipped_depth`.

- don't panic in the staging belt if the channel is dropped

- Crates:
- C API is moved to [another repository](https://github.com/gfx-rs/wgpu-native)
- `player`: standalone API replayer and tester
- Features:
- Proper error handling with all functions returning `Result`
- Graceful handling of "error" objects
- API tracing [infrastructure](http://kvark.github.io/wgpu/debug/test/ron/2020/07/18/wgpu-api-tracing.html)
- uploading data with `write_buffer`/`write_texture` queue operations
- reusable render bundles
- read-only depth/stencil attachments
- bind group layout deduplication
- Cows, cows everywhere
- Web+Native features:
- Depth clamping (feature)
- BC texture compression
- Native-only features:
- mappable primary buffers
- texture array bindings
- push constants
- multi-draw indirect
- Validation:
- all transfer operations
- all resource creation
- bind group matching to the layout
- experimental shader interface matching with Naga

wgpu-core-0.5.6 (2020-07-09)

- add debug markers support

wgpu-core-0.5.5 (2020-05-20)

- fix destruction of adapters, swap chains, and bind group layouts
- fix command pool leak with temporary threads
- improve assertion messages
- implement `From<TextureFormat>` for `TextureComponentType`

wgpu-core-0.5.4 (2020-04-24)

- fix memory management of staging buffers

wgpu-core-0.5.3 (2020-04-18)

- fix reading access to storage textures
- another fix to layout transitions for swapchain images

wgpu-core-0.5.2 (2020-04-15)

- fix read-only storage flags
- fix pipeline layout life time
- improve various assert messages

wgpu-core-0.5.1 (2020-04-10)

- fix tracking of swapchain images that are used multiple times in a command buffer
- fix tracking of initial usage of a resource across a command buffer