POSIX update and cleanups for getopt(3):

POSIX update and cleanups for getopt(3):

	o use getprogname(3) instead of using __progname directly;
	  the latter should only be used by {gs}etprogname(3).

	o handle strings with '--' correctly; this will display a
	  meaningful error when doing 'ls --color -l'.

	o correct behaviour with regard to POSIX; i.e., an error
	  message should be printed when the bad option is '?'.

Tested with 'buildworld' and 'installworld'; with and without
the change.

Obtained from FreeBSD and NetBSD.