Log Message:
openexr: Update to 2.4.0

Summary of changes:

    All code compiles without warnings on gcc, clang, msvc
    Cleanup of license and copyright notices
    floating-point exception handling is disabled by default
    New Slice::Make method to reliably compute base pointer for a slice.
    Miscellaneous bug fixes

This version fixes the following security vulnerabilities:

    CVE-2018-18444 Issue #351 Out of Memory
    CVE-2018-18443 Issue #350 heap-buffer-overflow