Base library for Industrial Light & Magic software (OpenEXR).

* Half is a class that encapsulates our 16-bit floating-point
format.

* IlmThread is a thread abstraction library for use with OpenEXR and
other software packages. It currently supports pthreads and
Windows threads.

* Imath implements 2D and 3D vectors, 3x3 and 4x4 matrices,
quaternions and other useful 2D and 3D math functions.

* Iex is an exception-handling library.