Zix 0.6.0

Zix 0.6.0 has been released. Zix is a lightweight C library of portability wrappers and data structures.

Changes:

• Add ZIX_NODISCARD attribute
• Add option to build for older Windows versions
• Add zix_expand_environment_strings()
• Add zix_string_view_equals()
• Avoid fdatasync() on Darwin
• Fix build on POSIX systems without PATH_MAX defined
• Fix library current_version on MacOS
• Fix nullability annotations for zix_canonical_path() and friends
• Fix ring unit test when mlock() is unavailable
• Improve documentation
• Support building for UWP
• Support building for Windows with or without UNICODE