Fix parsing of command-line arguments:

Fix parsing of command-line arguments:
- matching substrings won't work anymore (--receive-al won't match --receive),, I'm not
  sure at all this was intentional,
- fix and enhancement handling of mandatory and optional arguments to options (and fix
  their representation in --help),
- fix sub-arguments not being properly eaten by parser, then being parsed twice,
- -d is now an alias to --debug,
- avoid hardcoding strings length (fd_write, fd_write_all, strncmp), this is prone to error,
- more comprehensive error messages,
- man page content updates and fixes, format fixes and enhancements.