On systems where mdoc2man.pl is used, it puts the wrong name ("sftp" instead of
"ssh") into the ssh.1 man page. For example, under GatewayPorts: "By default,
sftp binds local port forwardings .... GatewayPorts can be used to specify that
sftp should bind local port forwardings ..."

The problem is that ssh.1 includes the following lines:

   when specifying configuration options using the
  .Nm ssh ,
  .Nm scp
  and
  .Nm sftp
  .Fl o
  option.

In mdoc2man.pl the line ".Nm sftp" sets $name to be "sftp" so subsequent
unqualified uses of ".Nm" produce "sftp" instead of "ssh".

The attached patch fixes the problem by not allowing $name to be redefined once
set.