rtemsbsd: Made TTCP command build for RTEMS

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.

libbsd.py

@@ -272,6 +272,7 @@ class rtems(builder.Module):
                 'rtems/rtems-bsd-shell-tcpdump.c',
                 'rtems/rtems-bsd-shell-vmstat.c',
                 'rtems/rtems-bsd-shell-wlanstats.c',
+                'rtems/rtems-bsd-shell-ttcp.c',
                 'rtems/rtems-kvm.c',
                 'rtems/rtems-program.c',
                 'rtems/rtems-program-socket.c',
@@ -295,6 +296,7 @@ class rtems(builder.Module):
                 'pppd/upap.c',
                 'pppd/utils.c',
                 'telnetd/telnetd-service.c',
+                'ttcp/ttcp.c',
             ],
             mm.generator['source']()
         )