main.c (main): POSIX states that getopt returns -1 when it is done

main.c (main): POSIX states that getopt returns -1 when it is done
	parsing options, not EOF.

configure.in: Use standard autoconf test names. Change tests to define
	standard autoconf CPP macro names, not the non-standard HAS_GETTOS,
	etc.

main.c, commands.c: Use HAVE_GETTOSBYNAME instead of HAS_GETTOS

ring.c, externs.h: Use HAVE_SYS_FILIO_H instead of FILIO_H

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@10570 dc483132-0cff-0310-8789-dd5450dbe970