Blender Git Loki

Merge branch 'master' into soc-2019-openxr

Avoid redundant framebuffer resize and offscreen texture drawing

Cleanup: Add comments

Address and remove some TODOs marked in code

Cleanup: Unused functions, add comments, sync to master

Improve batch file text for starting Blender with Oculus support

Don't create a DirectX swap-chain

We only render offscreen anyway. There's no point in creating a
swap-chain. This simplifies things quite a bit.

DirectX: Create an own render-target, don't use swapchain for blitting

Remove GHOST API functions for OpenGL offscreen blitting

These were previously used to blit from a offscreen (non-OpenGL)
context, into an onscreen one. We do this differently, and only within
GHOST_XrGraphicsBinding now, so this can be removed.

Refactor OpenGL/DirectX resource sharing for multiple shared resources

Rather than max. one shared resource per DirectX context, code can now
request a handle for a shared resource and ask the DirectX context to do
operations on that.

Fix missing CMake hint for OpenXR SDK path on linux

Windows/deps: Add/fix openxr_sdk dependency

There were a few typos here and there, and the openxr_sdk does not respect the cflags we give it hence a patch was added to work around this undesirable behaviour.

Merge branch 'master' into soc-2019-openxr

Fix compiling with WITH_OPENXR disabled

Blacklist VR add-on in Python tests if WITH_OPENXR is disabled

Expose WITH_OPENXR build option to Python API

Prepare Toggle VR Session operator to be enabled by an add-on

Windows: Print warning and disable `WITH_OPENXR` if SDK is not found

Integrate the OpenXR SDK better into dependency management

Adds the SDK so that `make deps` works, on all platforms. On Windows,
the SDK headers and libraries are now assumed to be in the usual lib
directory.
Also fixes a mistake in install_deps.sh

Note that none of this is tested as it requires an older Visual Studio
version than I have.

Fix compile error on Linux