Log Message:
imath: update to 3.1.7.

## Version 3.1.7 (March 1, 2023)

Patch release with miscellaneous bug/doc/build fixes. In particular:

- Support for relative prefix in pkg-config
- Reorganization of documentation at https://imath.readthedocs.io
- Add a ``trace()`` method on Matrix types

### Merged Pull Requests

*  Move index to bottom of main page; remove top-level link
*  Fix doc typo
*  Fix documentation glitches and symbol visibility table
*  Reorganize repo/readthedocs documentation
*  Add missing licenses/copyrights
*  Support relative prefix in pkg-config
*  Remove MACOSX_RPATH forcing
*  Add trace function for matrix types
*  Define BOOST_BIND_GLOBAL_PLACEHOLDERS to suppress pragma message
*  Use Py_ssize_t in place of size_t where appropriate to avoid warnings
*  Update CONTRIBUTING.md to be consistent with OpenEXR
*  Remove export attribute from inline half functions

## Version 3.1.6 (November 7, 2022)

Patch release with miscellaneous bug/doc/build fixes.

*  fix memory leak in V3fArrayFromBuffer
*  Add <cstdint> for int64_t
*  Initialize x in testRoots.cpp:solve() to suppress compiler warning
*  Fix gcc compiler warning in testFun.cpp
*  Test return value of extractSHRT to avoid uninitialized reference
*  Fix example code so it compiles as is
*  Cuda safety in several headers
*  Fix markdown and typos in README.md
*  Do not warn if half.h has already being included
*  Fix compiler warnings on windows
*  Remove irrelevant cvs ignore files
*  Update sphinx version