Lots of bugfixes, add the ENVIRON and X-DISPLAY-LOC

Lots of bugfixes, add the ENVIRON and X-DISPLAY-LOC
options, "-l user" to the command line, diagnostic flags.

SCCS-vsn: usr.bin/telnet/ring.c 1.13
SCCS-vsn: usr.bin/telnet/terminal.c 1.21
SCCS-vsn: usr.bin/telnet/network.c 1.15
SCCS-vsn: usr.bin/telnet/general.h 1.5
SCCS-vsn: usr.bin/telnet/ring.h 1.10
SCCS-vsn: usr.bin/telnet/externs.h 1.25
SCCS-vsn: usr.bin/telnet/tn3270.c 1.21
SCCS-vsn: usr.bin/telnet/telnet.c 5.50
SCCS-vsn: usr.bin/telnet/sys_bsd.c 1.27
SCCS-vsn: usr.bin/telnet/utilities.c 1.19
SCCS-vsn: usr.bin/telnet/telnet.1 6.10
SCCS-vsn: usr.bin/telnet/defines.h 1.10
SCCS-vsn: usr.bin/telnet/main.c 1.14
SCCS-vsn: usr.bin/telnet/commands.c 1.30
SCCS-vsn: usr.bin/telnet/Makefile 5.3
SCCS-vsn: libexec/telnetd/telnetd.c 5.45
SCCS-vsn: libexec/telnetd/telnetd.8 6.7
SCCS-vsn: libexec/telnetd/Makefile 5.10
SCCS-vsn: libexec/telnetd/defs.h 5.8
SCCS-vsn: libexec/telnetd/ext.h 5.6
SCCS-vsn: libexec/telnetd/pathnames.h 5.5
SCCS-vsn: libexec/telnetd/slc.c 5.4
SCCS-vsn: libexec/telnetd/state.c 5.7
SCCS-vsn: libexec/telnetd/sys_term.c 5.8
SCCS-vsn: libexec/telnetd/utility.c 5.4
SCCS-vsn: libexec/telnetd/termstat.c 5.6