Updated ttcp.c to build clean for RTEMS 6 and the machines it
originally built for. Also fixed ttcp.c to close network
sockets after completion. Defined a shell command for TTCP in
rtems-bsd-shell-ttcp.c. Added TTCP to the list of RTEMS network
commands in netcmds-config.h. Added declaration of the TTCP shell
command to rtems-bsd-commands.h. Modified libbsd.py to make waf
build TTCP and its shell command.