getopt: options struct, usage and version outputs

getopt: options struct, usage and version outputs

Move commands own option structure from global scope into main(),
and make it as read-only. The usage() ouput mechanims is made to
look more like other commands.

Misleading old version string `getopt (enhanced) 1.1.4' is
replaced to look like the other util-linux version outputs. If
anyone is relying on identifying the command by that string he
should use -T option instead.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>