Enable support for only 'long options'

Similar to POSIX's getopt_long() custom of using (CHAR_MAX+1) to
denote long options which have no short option equivalent,
allow specific (arbitrary) range of unicode characters to denote
long options.
(POSIX example: http://lingrok.org/xref/coreutils/src/sort.c#539 )

See tests for a usage example.