Many fixes. 1) Use the cc_t typedef from termios.h

Many fixes.  1) Use the cc_t typedef from termios.h
2) Fix for SYSV VEOF/VMIN overlap
3) Add two missing "break" statements
4) Add SLC_FORW[12] support
5) start of TOS support
6) Make sure things get initialized properly
7) Don't send Urgent mode data, since some clients go into infinate loops...

SCCS-vsn: libexec/telnetd/defs.h 5.4
SCCS-vsn: libexec/telnetd/ext.h 5.4
SCCS-vsn: libexec/telnetd/slc.c 5.2
SCCS-vsn: libexec/telnetd/state.c 5.5
SCCS-vsn: libexec/telnetd/sys_term.c 5.5
SCCS-vsn: libexec/telnetd/telnetd.c 5.42
SCCS-vsn: libexec/telnetd/termstat.c 5.4
SCCS-vsn: libexec/telnetd/Makefile 5.7