This is an initial commit for half texture support in Cycles.
It adds the basic infrastructure inside of the ImageManager and support for these textures on CPU.
Supported:
* Half Float OpenEXR images (can be used for e.g HDRs or Normalmaps) now use 1/2 the memory, when loaded via disk (OIIO).
ToDo:
Various things like support for inbuilt half textures, GPU... will come later, step by step.
Part of my GSoC 2016.
This makes OCIO viewport color correction a little bit faster (about -0.5s for 100 samples)
Also set max half float value to 65504.0 to conform with IEEE 754.
This makes the code a bit easier to understand, and might come in handy
if we want to reuse more Embree code.
Differential Revision: https://developer.blender.org/D482
Code by Brecht, with fixes by Lockal, Sergey and myself.
MSVC 2008 ignores alignement attribute when assigning from unaligned
float4 vector, returned from other function. Now Cycles uses unaligned
loads instead of casts for win32 in x86 mode.
