This adds the netstat command. All but one file is currently enabled.
That file does not currently build.
Also added libmemstat and libutil. libmemstat had a lot of code related
to kvm and kernel memory access disabled. This may or may not be an
issue.
The rtems shell commands should not exit but allow multiple
command attempts and some of the commands share code that
will exit. For this reason a common exit routine was
provided and code added to err.h to address this.
allow access to it.
This is enough to be able to invoke the ifconfig command but it
calls exit() which is inappropriate.
The "struct option" in the ifconfig code conflicts with a structure
of the same name in newlib's and glibc's getopt.h.
