ptyfwd: Set the size of the PTY base on the size of stdout, not stdin.
ptyfwd: Don't set the output prop of stdin, nor the input props of stdout.

It was calling cfmakeraw(3) on the properties for STDIN_FILENO; cfmakeraw
sets both input and output properties.  If (and only if) stdin and stdout
are the same device is this correct.  Otherwise, we must change only the
input properties of stdin, and only the output properties of stdout.