Unfs3 Versions Save

• switched to libtirpc as a base requirement
• contrib scripts now require Python 3 instead of Python 2
• fix stale handle when moving files or directories

NOTE: This is a retroactively tagged release for those interested in the last stable state before the migration to libtirpc.

• include AFS support for better serving of files from AFS filesystems
• use svc_getreq_poll() when available
• fix serving files larger than 4GB from Windows
• better support for 64-bit systems
• fixes for macOS and Windows support
• fixes when cross compiling
• better support for exporting FAT filesystems