When VIRGL_RENDERER_D3D11_SHARE_TEXTURE flag is set, and running on
ANGLE with D3D11 backend, virgl will try to allocate the texture itself,
with SHARED_NTHANDLE, and SHARED_KEYEDMUTEX. The texture is acquired
with key 0, so rendering can take place.

You can share the texture with a different process, thanks to
IDXGIResource1::CreateSharedHandle and DuplicateHandle. You must
properly handle the keyedmutex locking then between context/devices.

Similar to GBM buffer allocation, the texture used to create the
EGLImage and bind it to the GL texture.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: Gert Wollny <gert.wollny@collabora.com>
Part-of: <!1103>