New release series

• New stream for cleanups
• Drop support for 2.0 output & -C option
• Improve & fix recursive mode
• Drop old DEF_ERRNO support
• Drop DIRENT/SYSDIR config knobs
• Drop support for REGISTER build knob
• Drop support for explicit unaligned memory accesses
• Drop support for dead operating systems
• Fix Windows access fallback logic
• Include io.h on Windows
• Disable "deprecated" API warnings on Windows
• Add setmode binary for stdin and stdout on Windows
• Clean up help text a bit
• Add a standard -k (keep) option
• Use io.h fallbacks on mingw too