OpenColorIO: address review comments

Windows: OCIO2 build fixes

Nothing too interesting here, the static imports define
changed as did some of the library names/locations

OpenColorIO: remove default display workaround

A fix for this is in 2.0 (and recent 1.1.x versions), no need for this anymore.

OpenColorIO: update GPU display shader for version 2.0

To avoid baking exposure and gamma into the GLSL shader and requiring slow
recompiles when tweaking, we manually apply them in the shader. This leads
to some logic duplicaton between the CPU and GPU display processor, but it
seems unavoidable.

Caching was also changed. Previously this was done both on the imbuf and
opencolorio module levels. Now it's all done in the opencolorio module by
simply matching color space names. We no longer use cacheIDs from OpenColorIO
since computing them is expensive, and they are unlikely to match now that
more is baked into the shader code.

Shaders can now use multiple 2D textures, 3D textures and uniforms, rather
than a single 3D texture. So allocating and binding those adds some code.

Color space conversions for blending with overlays is now hardcoded in the
shader. This was using harcoded numbers anyway, if this every becomes a
general OpenColorIO transform it can be changed, but for now there is no
point to add code complexity.

OpenColorIO: use aces_interchange role to detect CIE XYZ values

We need standard CIE XYZ values for rendering effects like blackbody emission.
The relation to the scene linear role is based on OpenColorIO configuration.

In OpenColorIO 2.0 configs roles can no longer have the same name as color
spaces, which means our XYZ role and colorspace in the configuration give an
error.

Instead use the new standard aces_interchange role, which relates scene linear
to a known scene referred color space. Compatibility with the old XYZ role is
preserved, if the configuration file has no conflicting names.

Also includes a non-functional change to the configuraton file to use an
XYZ-to-ACES matrix instead of REC709-to-ACES, makes debugging a little easier
since the matrix is the same one we have in the code now and that is also
found easily in the ACES specs.

There is a new cie_xyz_d65_interchange role that we should add support for,
for interchange of display referred colorspace (as opposed to scene referred).
I couldn't immediately understand how that is supposed to be defined, will
probably leave that for another patch unless someone knows how.

OpenColorIO: update display transforms for version 2.0

Needs a bit more manual work constructing the transform. LegacyViewingPipeline
could also have been used, but isn't really any simpler and since it's legacy
we better not rely on it.

This moves more logic into the opencolorio module, to simplify the API. There is
no need to wrap a dozen functions just to be able to do this in C rather than C++.
It's also tightly coupled to the GPU shader logic, and so should be in the same
module.

OpenColorIO: update processors and transforms for version 2.0

CPU processors now need to be created to do CPU processing. These are cached
internally, but the cache lookup is not fast enough to execute per pixel or
texture sample, so for performance these are now also exposed in the C API.

The C API for transform will no longer be needed afer all changes, so remove
it to simplify the API and fallback implementation.

Build: OpenColorIO 2.0.0 support for make deps and install_deps.sh

* Tinyxml was replaced with Expat, adding a new dependency.
* Yaml-cpp is now built as a dependency on Unix, as was already done on Windows.
* Removed currently unused LCMS code, couldn't be bothered to update and test it.
* Pystring remains built as part of OCIO itself, since it has no good build system.

We currently require OpenColorIO 2.0.0 and the upcoming code changes have no
compatibility with 1.x. Compatibility could be added, but it's rather complicated
and I only want to do the work if it's really needed.

The install_deps.sh support was implemented by Jeroen, I have no tested it myself.

The Windows code was updated, but I have not tested if it actually works, it
almost certainly will not.