* Adds UAV support for D3D12, Vulkan and reworked support for OpenGL, D3D11
UAV support is now uniform across compute and draw.
To set a UAV you just use bgfx::setImage() and IMAGE2D in the shader, just like in compute.
Due to these changes shaders will have to be recompiled.
The changes include:
- D3D11 requires patching of the UAV slot number (which is now done by modifying the DXBC instead of using a macro)
- If the DXBC binary includes a debug chunk, that is also patched to match the new slot number
- All the other renderers don't need any kind of patching
- There are some shader annotations to better convert the UAV format used in hlsl to spirv
Possibility of further enhancements:
- bgfx::setViewFrameBuffer() only supports binding to a framebuffer or, using BGFX_INVALID_HANDLE, to bind the default backbuffer. This doesn't allow for the case where there is no need to bind to either one of them, for example when using a fragment shader only to read and write to an UAV.
* Bump shader version, because they need to be recompiled.
* view stats: Make GPU begin and end times available
* view stats: Make CPU start and end times available
* view stats: Remove redundant `gpuTimeElapsed`
Value can be derived by `gpuTimeEnd - gpuTimeBegin`
* view stats: Remove redundant `cpuTimeElapsed`
Value can be derived by `cpuTimeEnd - cpuTimeBegin`
