Log message:
imath: update to 3.1.5.

## Version 3.1.5 (March 28, 2022)

Patch release with miscellaneous bug/doc/build fixes.

In particular, this fixes an issue that could lead to incorrect values
for `numeric_limits<half>`. This also updates the CI workflow matrix
to VFX-CY2022.

Log message:
imath: update to 3.1.4.

## Version 3.1.4 (January 21, 2022)

Patch release with miscellaneous bug/doc/build fixes.

Log message:
math: Replace RMD160 checksums with BLAKE2s checksums

All checksums have been double-checked against existing RMD160 and
SHA512 hashes

Log message:
math: Remove SHA1 hashes for distfiles

Log message:
imath: update to 3.1.3.

## Version 3.1.3 (September 2, 2021)

Patch release with miscellaneous fixes

* Fix undefined access of a vector when empty
* Require sphinx 4.0.3
* Build sphinx/doxygen docs with CMake
* Use PYIMATH_OVERRIDE_PYTHON_INSTALL_DIR to specify destination python modules
* Guard `__has_attribute` for compilers that don't support it
* Cuda safety fixes
* Replace stray Imath:: with IMATH_INTERNAL_NAMESPACE::

Log message:
imath: update to 3.1.2.

## Version 3.1.2 (July 31, 2021)

Patch release that fixes a Windows header issue.

* Improve handling of ``#include <*intrin.h>``

## Version 3.1.1 (July 20, 2021)

Patch release that fixes a build failure on ARM64 macOS

## Version 3.1.0 (July 13, 2021)

Minor release with new features:

* Optimized half-to-float and float-to-half conversion, using F16C SSE
  instruction set if available. Non-SSE conversion eliminates the
  float-to-half exponent lookup table, and half-to-float conversion
  provides a compile-time-optional bit shifting that is slower but
  eliminates the need for the lookup table, for applications where
  memory is limited.

  Half-to-float and float-to-half conversion is also available as
  C-language functions ``imath_half_to_float()`` and
  ``imath_float_to_half()``.

  All new conversions produced identical results, and new options are
  off by default to ensure backwards compatibility. See
  https://imath.readthedocs.io for more info.

* NOEXCEPT specifier can be eliminated at compile-time via the
  ``IMATH_USE_NOEXCEPT`` CMake option.

* Python bindings:
  * FixedArray objects support a "read only" state.
  * FixedArray objects support python buffer protocol.

* Optimized 4x4 matrix multiplication.

Log message:
imath: add version 3.0.5

Imath is a basic, light-weight, and efficient C++ representation of 2D
and 3D vectors and matrices and other simple but useful mathematical
objects, functions, and data types common in computer graphics
applications.