Busybox echo prints error messages

It was ignoring any errors, depending on which version of echo_main was
being built.  It's a minor pain to detect errors too, due to how glibc
implements fputs, I think.  Clearing and checking errno suffices.

Now, when you echo garbage > /some/9ns/ctlfile, you'll hear about what
went wrong.

If we start building with writev, or whatever, then we may need another
patch.

You'll need to patch busybox, etc.
Cleaned up some printking

The ifconfig is a bit tricky.  Somewhere we set errno in the kernel,
probably during the various bind internal calls.  It's probably fine,
but my BB echo hacks thinks it is an error.

The kprof extra printk isn't needed since echo now prints errors.