Log Message:
openexr: update to 3.1.1.

## Version 3.1.1 (August 2, 2021)

Patch release that fixes build failures on various systems, introduces
CMake ``CMAKE_CROSSCOMPILING_EMULATOR`` support, and fixes a few other
minor issues.

## Version 3.1.0 (July 22, 2021)

The 3.1 release of OpenEXR introduces a new library, OpenEXRCore,
which is the result of a significant re-thinking of how OpenEXR
manages file I/O and provides access to image data. It begins to
address long-standing scalability issues with multithreaded image
reading and writing.

The OpenEXRCore library provides thread-safe, non-blocking access to
files, which was not possible with the current API, where the
framebuffer management is separate from read requests. It is written
entirely in C and provides a new C-language API alongside the existing
C++ API. This new low-level API allows applications to do custom
unpacking of EXR data, such as on the GPU, while still benefiting from
efficient I/O, file validation, and other semantics. It provides
efficient direct access to EXR files in texturing applications. This C
library also introduces an easier path to implementing OpenEXR
bindings in other languages, such as Rust.

The 3.1 release represents a technology preview for upcoming
releases. The initial release is incremental; the existing API and
underlying behavior has not changed. The new API is available now for
performance validation testing, and then in future OpenEXR releases,
the C++ API will migrate to use the new core in stages.  It is not the
intention to entirely deprecate the C++ API, nor must all applications
re-implement EXR I/O in terms of the C library. The C API does not,
and will not, provide the rich set of utility classes that exist in
the C++ layer. The 3.1 release of the OpenEXRCore library simply
offers new functionality for specialty applications seeking the
highest possible performance. In the future, the ABI will evolve, but
the API will remain consistent, or only have additions.