Feature removal: bug compatibility code, and --ssh1-fallback

I'm considering removing the bug compatibility code needed for
interoperability with Datafellows/SSH ssh versions 2.0.x, 2.1.0 and
3.0.

I'm also considering removing the --ssh1-fallback feature from lshd.

If anybody uses and needs these feature, please speak up.

Regards,
/Niels